From 7b02207537d35bfa1714bf8beafc921f717d100a Mon Sep 17 00:00:00 2001
From: 单军华
Date: Wed, 11 Jul 2018 10:47:42 +0800
Subject: [PATCH] 首次上传

---
 screendisplay/Pods/YYImage/YYImage/YYImageCoder.m | 2870 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 2,870 insertions(+), 0 deletions(-)

diff --git a/screendisplay/Pods/YYImage/YYImage/YYImageCoder.m b/screendisplay/Pods/YYImage/YYImage/YYImageCoder.m
new file mode 100755
index 0000000..66cf46e
--- /dev/null
+++ b/screendisplay/Pods/YYImage/YYImage/YYImageCoder.m
@@ -0,0 +1,2870 @@
+//
+//  YYImageCoder.m
+//  YYImage <https://github.com/ibireme/YYImage>
+//
+//  Created by ibireme on 15/5/13.
+//  Copyright (c) 2015 ibireme.
+//
+//  This source code is licensed under the MIT-style license found in the
+//  LICENSE file in the root directory of this source tree.
+//
+
+#import "YYImageCoder.h"
+#import "YYImage.h"
+#import <CoreFoundation/CoreFoundation.h>
+#import <ImageIO/ImageIO.h>
+#import <Accelerate/Accelerate.h>
+#import <QuartzCore/QuartzCore.h>
+#import <MobileCoreServices/MobileCoreServices.h>
+#import <AssetsLibrary/AssetsLibrary.h>
+#import <objc/runtime.h>
+#import <pthread.h>
+#import <zlib.h>
+
+
+
+#ifndef YYIMAGE_WEBP_ENABLED
+#if __has_include(<webp/decode.h>) && __has_include(<webp/encode.h>) && \
+    __has_include(<webp/demux.h>)  && __has_include(<webp/mux.h>)
+#define YYIMAGE_WEBP_ENABLED 1
+#import <webp/decode.h>
+#import <webp/encode.h>
+#import <webp/demux.h>
+#import <webp/mux.h>
+#elif __has_include("webp/decode.h") && __has_include("webp/encode.h") && \
+      __has_include("webp/demux.h")  && __has_include("webp/mux.h")
+#define YYIMAGE_WEBP_ENABLED 1
+#import "webp/decode.h"
+#import "webp/encode.h"
+#import "webp/demux.h"
+#import "webp/mux.h"
+#else
+#define YYIMAGE_WEBP_ENABLED 0
+#endif
+#endif
+
+
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+#pragma mark - Utility (for little endian platform)
+
+#define YY_FOUR_CC(c1,c2,c3,c4) ((uint32_t)(((c4) << 24) | ((c3) << 16) | ((c2) << 8) | (c1)))
+#define YY_TWO_CC(c1,c2) ((uint16_t)(((c2) << 8) | (c1)))
+
+static inline uint16_t yy_swap_endian_uint16(uint16_t value) {
+    return
+    (uint16_t) ((value & 0x00FF) << 8) |
+    (uint16_t) ((value & 0xFF00) >> 8) ;
+}
+
+static inline uint32_t yy_swap_endian_uint32(uint32_t value) {
+    return
+    (uint32_t)((value & 0x000000FFU) << 24) |
+    (uint32_t)((value & 0x0000FF00U) <<  8) |
+    (uint32_t)((value & 0x00FF0000U) >>  8) |
+    (uint32_t)((value & 0xFF000000U) >> 24) ;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+#pragma mark - APNG
+
+/*
+ PNG  spec: http://www.libpng.org/pub/png/spec/1.2/PNG-Structure.html
+ APNG spec: https://wiki.mozilla.org/APNG_Specification
+ 
+ ===============================================================================
+ PNG format:
+ header (8): 89 50 4e 47 0d 0a 1a 0a
+ chunk, chunk, chunk, ...
+ 
+ ===============================================================================
+ chunk format:
+ length (4): uint32_t big endian
+ fourcc (4): chunk type code
+ data   (length): data
+ crc32  (4): uint32_t big endian crc32(fourcc + data)
+ 
+ ===============================================================================
+ PNG chunk define:
+ 
+ IHDR (Image Header) required, must appear first, 13 bytes
+ width              (4) pixel count, should not be zero
+ height             (4) pixel count, should not be zero
+ bit depth          (1) expected: 1, 2, 4, 8, 16
+ color type         (1) 1<<0 (palette used), 1<<1 (color used), 1<<2 (alpha channel used)
+ compression method (1) 0 (deflate/inflate)
+ filter method      (1) 0 (adaptive filtering with five basic filter types)
+ interlace method   (1) 0 (no interlace) or 1 (Adam7 interlace)
+ 
+ IDAT (Image Data) required, must appear consecutively if there's multiple 'IDAT' chunk
+ 
+ IEND (End) required, must appear last, 0 bytes
+ 
+ ===============================================================================
+ APNG chunk define:
+ 
+ acTL (Animation Control) required, must appear before 'IDAT', 8 bytes
+ num frames     (4) number of frames
+ num plays      (4) number of times to loop, 0 indicates infinite looping
+ 
+ fcTL (Frame Control) required, must appear before the 'IDAT' or 'fdAT' chunks of the frame to which it applies, 26 bytes
+ sequence number   (4) sequence number of the animation chunk, starting from 0
+ width             (4) width of the following frame
+ height            (4) height of the following frame
+ x offset          (4) x position at which to render the following frame
+ y offset          (4) y position at which to render the following frame
+ delay num         (2) frame delay fraction numerator
+ delay den         (2) frame delay fraction denominator
+ dispose op        (1) type of frame area disposal to be done after rendering this frame (0:none, 1:background 2:previous)
+ blend op          (1) type of frame area rendering for this frame (0:source, 1:over)
+ 
+ fdAT (Frame Data) required
+ sequence number   (4) sequence number of the animation chunk
+ frame data        (x) frame data for this frame (same as 'IDAT')
+ 
+ ===============================================================================
+ `dispose_op` specifies how the output buffer should be changed at the end of the delay 
+ (before rendering the next frame).
+ 
+ * NONE: no disposal is done on this frame before rendering the next; the contents
+    of the output buffer are left as is.
+ * BACKGROUND: the frame's region of the output buffer is to be cleared to fully
+    transparent black before rendering the next frame.
+ * PREVIOUS: the frame's region of the output buffer is to be reverted to the previous
+    contents before rendering the next frame.
+
+ `blend_op` specifies whether the frame is to be alpha blended into the current output buffer
+ content, or whether it should completely replace its region in the output buffer.
+ 
+ * SOURCE: all color components of the frame, including alpha, overwrite the current contents
+    of the frame's output buffer region. 
+ * OVER: the frame should be composited onto the output buffer based on its alpha,
+    using a simple OVER operation as described in the "Alpha Channel Processing" section
+    of the PNG specification
+ */
+
+typedef enum {
+    YY_PNG_ALPHA_TYPE_PALEETE = 1 << 0,
+    YY_PNG_ALPHA_TYPE_COLOR = 1 << 1,
+    YY_PNG_ALPHA_TYPE_ALPHA = 1 << 2,
+} yy_png_alpha_type;
+
+typedef enum {
+    YY_PNG_DISPOSE_OP_NONE = 0,
+    YY_PNG_DISPOSE_OP_BACKGROUND = 1,
+    YY_PNG_DISPOSE_OP_PREVIOUS = 2,
+} yy_png_dispose_op;
+
+typedef enum {
+    YY_PNG_BLEND_OP_SOURCE = 0,
+    YY_PNG_BLEND_OP_OVER = 1,
+} yy_png_blend_op;
+
+typedef struct {
+    uint32_t width;             ///< pixel count, should not be zero
+    uint32_t height;            ///< pixel count, should not be zero
+    uint8_t bit_depth;          ///< expected: 1, 2, 4, 8, 16
+    uint8_t color_type;         ///< see yy_png_alpha_type
+    uint8_t compression_method; ///< 0 (deflate/inflate)
+    uint8_t filter_method;      ///< 0 (adaptive filtering with five basic filter types)
+    uint8_t interlace_method;   ///< 0 (no interlace) or 1 (Adam7 interlace)
+} yy_png_chunk_IHDR;
+
+typedef struct {
+    uint32_t sequence_number;  ///< sequence number of the animation chunk, starting from 0
+    uint32_t width;            ///< width of the following frame
+    uint32_t height;           ///< height of the following frame
+    uint32_t x_offset;         ///< x position at which to render the following frame
+    uint32_t y_offset;         ///< y position at which to render the following frame
+    uint16_t delay_num;        ///< frame delay fraction numerator
+    uint16_t delay_den;        ///< frame delay fraction denominator
+    uint8_t dispose_op;        ///< see yy_png_dispose_op
+    uint8_t blend_op;          ///< see yy_png_blend_op
+} yy_png_chunk_fcTL;
+
+typedef struct {
+    uint32_t offset; ///< chunk offset in PNG data
+    uint32_t fourcc; ///< chunk fourcc
+    uint32_t length; ///< chunk data length
+    uint32_t crc32;  ///< chunk crc32
+} yy_png_chunk_info;
+
+typedef struct {
+    uint32_t chunk_index; ///< the first `fdAT`/`IDAT` chunk index
+    uint32_t chunk_num;   ///< the `fdAT`/`IDAT` chunk count
+    uint32_t chunk_size;  ///< the `fdAT`/`IDAT` chunk bytes
+    yy_png_chunk_fcTL frame_control;
+} yy_png_frame_info;
+
+typedef struct {
+    yy_png_chunk_IHDR header;   ///< png header
+    yy_png_chunk_info *chunks;      ///< chunks
+    uint32_t chunk_num;          ///< count of chunks
+    
+    yy_png_frame_info *apng_frames; ///< frame info, NULL if not apng
+    uint32_t apng_frame_num;     ///< 0 if not apng
+    uint32_t apng_loop_num;      ///< 0 indicates infinite looping
+    
+    uint32_t *apng_shared_chunk_indexs; ///< shared chunk index
+    uint32_t apng_shared_chunk_num;     ///< shared chunk count
+    uint32_t apng_shared_chunk_size;    ///< shared chunk bytes
+    uint32_t apng_shared_insert_index;  ///< shared chunk insert index
+    bool apng_first_frame_is_cover;     ///< the first frame is same as png (cover)
+} yy_png_info;
+
+static void yy_png_chunk_IHDR_read(yy_png_chunk_IHDR *IHDR, const uint8_t *data) {
+    IHDR->width = yy_swap_endian_uint32(*((uint32_t *)(data)));
+    IHDR->height = yy_swap_endian_uint32(*((uint32_t *)(data + 4)));
+    IHDR->bit_depth = data[8];
+    IHDR->color_type = data[9];
+    IHDR->compression_method = data[10];
+    IHDR->filter_method = data[11];
+    IHDR->interlace_method = data[12];
+}
+
+static void yy_png_chunk_IHDR_write(yy_png_chunk_IHDR *IHDR, uint8_t *data) {
+    *((uint32_t *)(data)) = yy_swap_endian_uint32(IHDR->width);
+    *((uint32_t *)(data + 4)) = yy_swap_endian_uint32(IHDR->height);
+    data[8] = IHDR->bit_depth;
+    data[9] = IHDR->color_type;
+    data[10] = IHDR->compression_method;
+    data[11] = IHDR->filter_method;
+    data[12] = IHDR->interlace_method;
+}
+
+static void yy_png_chunk_fcTL_read(yy_png_chunk_fcTL *fcTL, const uint8_t *data) {
+    fcTL->sequence_number = yy_swap_endian_uint32(*((uint32_t *)(data)));
+    fcTL->width = yy_swap_endian_uint32(*((uint32_t *)(data + 4)));
+    fcTL->height = yy_swap_endian_uint32(*((uint32_t *)(data + 8)));
+    fcTL->x_offset = yy_swap_endian_uint32(*((uint32_t *)(data + 12)));
+    fcTL->y_offset = yy_swap_endian_uint32(*((uint32_t *)(data + 16)));
+    fcTL->delay_num = yy_swap_endian_uint16(*((uint16_t *)(data + 20)));
+    fcTL->delay_den = yy_swap_endian_uint16(*((uint16_t *)(data + 22)));
+    fcTL->dispose_op = data[24];
+    fcTL->blend_op = data[25];
+}
+
+static void yy_png_chunk_fcTL_write(yy_png_chunk_fcTL *fcTL, uint8_t *data) {
+    *((uint32_t *)(data)) = yy_swap_endian_uint32(fcTL->sequence_number);
+    *((uint32_t *)(data + 4)) = yy_swap_endian_uint32(fcTL->width);
+    *((uint32_t *)(data + 8)) = yy_swap_endian_uint32(fcTL->height);
+    *((uint32_t *)(data + 12)) = yy_swap_endian_uint32(fcTL->x_offset);
+    *((uint32_t *)(data + 16)) = yy_swap_endian_uint32(fcTL->y_offset);
+    *((uint16_t *)(data + 20)) = yy_swap_endian_uint16(fcTL->delay_num);
+    *((uint16_t *)(data + 22)) = yy_swap_endian_uint16(fcTL->delay_den);
+    data[24] = fcTL->dispose_op;
+    data[25] = fcTL->blend_op;
+}
+
+// convert double value to fraction
+static void yy_png_delay_to_fraction(double duration, uint16_t *num, uint16_t *den) {
+    if (duration >= 0xFF) {
+        *num = 0xFF;
+        *den = 1;
+    } else if (duration <= 1.0 / (double)0xFF) {
+        *num = 1;
+        *den = 0xFF;
+    } else {
+        // Use continued fraction to calculate the num and den.
+        long MAX = 10;
+        double eps = (0.5 / (double)0xFF);
+        long p[MAX], q[MAX], a[MAX], i, numl = 0, denl = 0;
+        // The first two convergents are 0/1 and 1/0
+        p[0] = 0; q[0] = 1;
+        p[1] = 1; q[1] = 0;
+        // The rest of the convergents (and continued fraction)
+        for (i = 2; i < MAX; i++) {
+            a[i] = lrint(floor(duration));
+            p[i] = a[i] * p[i - 1] + p[i - 2];
+            q[i] = a[i] * q[i - 1] + q[i - 2];
+            if (p[i] <= 0xFF && q[i] <= 0xFF) { // uint16_t
+                numl = p[i];
+                denl = q[i];
+            } else break;
+            if (fabs(duration - a[i]) < eps) break;
+            duration = 1.0 / (duration - a[i]);
+        }
+        
+        if (numl != 0 && denl != 0) {
+            *num = numl;
+            *den = denl;
+        } else {
+            *num = 1;
+            *den = 100;
+        }
+    }
+}
+
+// convert fraction to double value
+static double yy_png_delay_to_seconds(uint16_t num, uint16_t den) {
+    if (den == 0) {
+        return num / 100.0;
+    } else {
+        return (double)num / (double)den;
+    }
+}
+
+static bool yy_png_validate_animation_chunk_order(yy_png_chunk_info *chunks,  /* input */
+                                                  uint32_t chunk_num,         /* input */
+                                                  uint32_t *first_idat_index, /* output */
+                                                  bool *first_frame_is_cover  /* output */) {
+    /*
+     PNG at least contains 3 chunks: IHDR, IDAT, IEND.
+     `IHDR` must appear first.
+     `IDAT` must appear consecutively.
+     `IEND` must appear end.
+     
+     APNG must contains one `acTL` and at least one 'fcTL' and `fdAT`.
+     `fdAT` must appear consecutively.
+     `fcTL` must appear before `IDAT` or `fdAT`.
+     */
+    if (chunk_num <= 2) return false;
+    if (chunks->fourcc != YY_FOUR_CC('I', 'H', 'D', 'R')) return false;
+    if ((chunks + chunk_num - 1)->fourcc != YY_FOUR_CC('I', 'E', 'N', 'D')) return false;
+    
+    uint32_t prev_fourcc = 0;
+    uint32_t IHDR_num = 0;
+    uint32_t IDAT_num = 0;
+    uint32_t acTL_num = 0;
+    uint32_t fcTL_num = 0;
+    uint32_t first_IDAT = 0;
+    bool first_frame_cover = false;
+    for (uint32_t i = 0; i < chunk_num; i++) {
+        yy_png_chunk_info *chunk = chunks + i;
+        switch (chunk->fourcc) {
+            case YY_FOUR_CC('I', 'H', 'D', 'R'): {  // png header
+                if (i != 0) return false;
+                if (IHDR_num > 0) return false;
+                IHDR_num++;
+            } break;
+            case YY_FOUR_CC('I', 'D', 'A', 'T'): {  // png data
+                if (prev_fourcc != YY_FOUR_CC('I', 'D', 'A', 'T')) {
+                    if (IDAT_num == 0)
+                        first_IDAT = i;
+                    else
+                        return false;
+                }
+                IDAT_num++;
+            } break;
+            case YY_FOUR_CC('a', 'c', 'T', 'L'): {  // apng control
+                if (acTL_num > 0) return false;
+                acTL_num++;
+            } break;
+            case YY_FOUR_CC('f', 'c', 'T', 'L'): {  // apng frame control
+                if (i + 1 == chunk_num) return false;
+                if ((chunk + 1)->fourcc != YY_FOUR_CC('f', 'd', 'A', 'T') &&
+                    (chunk + 1)->fourcc != YY_FOUR_CC('I', 'D', 'A', 'T')) {
+                    return false;
+                }
+                if (fcTL_num == 0) {
+                    if ((chunk + 1)->fourcc == YY_FOUR_CC('I', 'D', 'A', 'T')) {
+                        first_frame_cover = true;
+                    }
+                }
+                fcTL_num++;
+            } break;
+            case YY_FOUR_CC('f', 'd', 'A', 'T'): {  // apng data
+                if (prev_fourcc != YY_FOUR_CC('f', 'd', 'A', 'T') && prev_fourcc != YY_FOUR_CC('f', 'c', 'T', 'L')) {
+                    return false;
+                }
+            } break;
+        }
+        prev_fourcc = chunk->fourcc;
+    }
+    if (IHDR_num != 1) return false;
+    if (IDAT_num == 0) return false;
+    if (acTL_num != 1) return false;
+    if (fcTL_num < acTL_num) return false;
+    *first_idat_index = first_IDAT;
+    *first_frame_is_cover = first_frame_cover;
+    return true;
+}
+
+static void yy_png_info_release(yy_png_info *info) {
+    if (info) {
+        if (info->chunks) free(info->chunks);
+        if (info->apng_frames) free(info->apng_frames);
+        if (info->apng_shared_chunk_indexs) free(info->apng_shared_chunk_indexs);
+        free(info);
+    }
+}
+
+/**
+ Create a png info from a png file. See struct png_info for more information.
+ 
+ @param data   png/apng file data.
+ @param length the data's length in bytes.
+ @return A png info object, you may call yy_png_info_release() to release it.
+ Returns NULL if an error occurs.
+ */
+static yy_png_info *yy_png_info_create(const uint8_t *data, uint32_t length) {
+    if (length < 32) return NULL;
+    if (*((uint32_t *)data) != YY_FOUR_CC(0x89, 0x50, 0x4E, 0x47)) return NULL;
+    if (*((uint32_t *)(data + 4)) != YY_FOUR_CC(0x0D, 0x0A, 0x1A, 0x0A)) return NULL;
+    
+    uint32_t chunk_realloc_num = 16;
+    yy_png_chunk_info *chunks = malloc(sizeof(yy_png_chunk_info) * chunk_realloc_num);
+    if (!chunks) return NULL;
+    
+    // parse png chunks
+    uint32_t offset = 8;
+    uint32_t chunk_num = 0;
+    uint32_t chunk_capacity = chunk_realloc_num;
+    uint32_t apng_loop_num = 0;
+    int32_t apng_sequence_index = -1;
+    int32_t apng_frame_index = 0;
+    int32_t apng_frame_number = -1;
+    bool apng_chunk_error = false;
+    do {
+        if (chunk_num >= chunk_capacity) {
+            yy_png_chunk_info *new_chunks = realloc(chunks, sizeof(yy_png_chunk_info) * (chunk_capacity + chunk_realloc_num));
+            if (!new_chunks) {
+                free(chunks);
+                return NULL;
+            }
+            chunks = new_chunks;
+            chunk_capacity += chunk_realloc_num;
+        }
+        yy_png_chunk_info *chunk = chunks + chunk_num;
+        const uint8_t *chunk_data = data + offset;
+        chunk->offset = offset;
+        chunk->length = yy_swap_endian_uint32(*((uint32_t *)chunk_data));
+        if ((uint64_t)chunk->offset + (uint64_t)chunk->length + 12 > length) {
+            free(chunks);
+            return NULL;
+        }
+        
+        chunk->fourcc = *((uint32_t *)(chunk_data + 4));
+        if ((uint64_t)chunk->offset + 4 + chunk->length + 4 > (uint64_t)length) break;
+        chunk->crc32 = yy_swap_endian_uint32(*((uint32_t *)(chunk_data + 8 + chunk->length)));
+        chunk_num++;
+        offset += 12 + chunk->length;
+        
+        switch (chunk->fourcc) {
+            case YY_FOUR_CC('a', 'c', 'T', 'L') : {
+                if (chunk->length == 8) {
+                    apng_frame_number = yy_swap_endian_uint32(*((uint32_t *)(chunk_data + 8)));
+                    apng_loop_num = yy_swap_endian_uint32(*((uint32_t *)(chunk_data + 12)));
+                } else {
+                    apng_chunk_error = true;
+                }
+            } break;
+            case YY_FOUR_CC('f', 'c', 'T', 'L') :
+            case YY_FOUR_CC('f', 'd', 'A', 'T') : {
+                if (chunk->fourcc == YY_FOUR_CC('f', 'c', 'T', 'L')) {
+                    if (chunk->length != 26) {
+                        apng_chunk_error = true;
+                    } else {
+                        apng_frame_index++;
+                    }
+                }
+                if (chunk->length > 4) {
+                    uint32_t sequence = yy_swap_endian_uint32(*((uint32_t *)(chunk_data + 8)));
+                    if (apng_sequence_index + 1 == sequence) {
+                        apng_sequence_index++;
+                    } else {
+                        apng_chunk_error = true;
+                    }
+                } else {
+                    apng_chunk_error = true;
+                }
+            } break;
+            case YY_FOUR_CC('I', 'E', 'N', 'D') : {
+                offset = length; // end, break do-while loop
+            } break;
+        }
+    } while (offset + 12 <= length);
+    
+    if (chunk_num < 3 ||
+        chunks->fourcc != YY_FOUR_CC('I', 'H', 'D', 'R') ||
+        chunks->length != 13) {
+        free(chunks);
+        return NULL;
+    }
+    
+    // png info
+    yy_png_info *info = calloc(1, sizeof(yy_png_info));
+    if (!info) {
+        free(chunks);
+        return NULL;
+    }
+    info->chunks = chunks;
+    info->chunk_num = chunk_num;
+    yy_png_chunk_IHDR_read(&info->header, data + chunks->offset + 8);
+    
+    // apng info
+    if (!apng_chunk_error && apng_frame_number == apng_frame_index && apng_frame_number >= 1) {
+        bool first_frame_is_cover = false;
+        uint32_t first_IDAT_index = 0;
+        if (!yy_png_validate_animation_chunk_order(info->chunks, info->chunk_num, &first_IDAT_index, &first_frame_is_cover)) {
+            return info; // ignore apng chunk
+        }
+        
+        info->apng_loop_num = apng_loop_num;
+        info->apng_frame_num = apng_frame_number;
+        info->apng_first_frame_is_cover = first_frame_is_cover;
+        info->apng_shared_insert_index = first_IDAT_index;
+        info->apng_frames = calloc(apng_frame_number, sizeof(yy_png_frame_info));
+        if (!info->apng_frames) {
+            yy_png_info_release(info);
+            return NULL;
+        }
+        info->apng_shared_chunk_indexs = calloc(info->chunk_num, sizeof(uint32_t));
+        if (!info->apng_shared_chunk_indexs) {
+            yy_png_info_release(info);
+            return NULL;
+        }
+        
+        int32_t frame_index = -1;
+        uint32_t *shared_chunk_index = info->apng_shared_chunk_indexs;
+        for (int32_t i = 0; i < info->chunk_num; i++) {
+            yy_png_chunk_info *chunk = info->chunks + i;
+            switch (chunk->fourcc) {
+                case YY_FOUR_CC('I', 'D', 'A', 'T'): {
+                    if (info->apng_shared_insert_index == 0) {
+                        info->apng_shared_insert_index = i;
+                    }
+                    if (first_frame_is_cover) {
+                        yy_png_frame_info *frame = info->apng_frames + frame_index;
+                        frame->chunk_num++;
+                        frame->chunk_size += chunk->length + 12;
+                    }
+                } break;
+                case YY_FOUR_CC('a', 'c', 'T', 'L'): {
+                } break;
+                case YY_FOUR_CC('f', 'c', 'T', 'L'): {
+                    frame_index++;
+                    yy_png_frame_info *frame = info->apng_frames + frame_index;
+                    frame->chunk_index = i + 1;
+                    yy_png_chunk_fcTL_read(&frame->frame_control, data + chunk->offset + 8);
+                } break;
+                case YY_FOUR_CC('f', 'd', 'A', 'T'): {
+                    yy_png_frame_info *frame = info->apng_frames + frame_index;
+                    frame->chunk_num++;
+                    frame->chunk_size += chunk->length + 12;
+                } break;
+                default: {
+                    *shared_chunk_index = i;
+                    shared_chunk_index++;
+                    info->apng_shared_chunk_size += chunk->length + 12;
+                    info->apng_shared_chunk_num++;
+                } break;
+            }
+        }
+    }
+    return info;
+}
+
+/**
+ Copy a png frame data from an apng file.
+ 
+ @param data  apng file data
+ @param info  png info
+ @param index frame index (zero-based)
+ @param size  output, the size of the frame data
+ @return A frame data (single-frame png file), call free() to release the data.
+ Returns NULL if an error occurs.
+ */
+static uint8_t *yy_png_copy_frame_data_at_index(const uint8_t *data,
+                                                const yy_png_info *info,
+                                                const uint32_t index,
+                                                uint32_t *size) {
+    if (index >= info->apng_frame_num) return NULL;
+    
+    yy_png_frame_info *frame_info = info->apng_frames + index;
+    uint32_t frame_remux_size = 8 /* PNG Header */ + info->apng_shared_chunk_size + frame_info->chunk_size;
+    if (!(info->apng_first_frame_is_cover && index == 0)) {
+        frame_remux_size -= frame_info->chunk_num * 4; // remove fdAT sequence number
+    }
+    uint8_t *frame_data = malloc(frame_remux_size);
+    if (!frame_data) return NULL;
+    *size = frame_remux_size;
+    
+    uint32_t data_offset = 0;
+    bool inserted = false;
+    memcpy(frame_data, data, 8); // PNG File Header
+    data_offset += 8;
+    for (uint32_t i = 0; i < info->apng_shared_chunk_num; i++) {
+        uint32_t shared_chunk_index = info->apng_shared_chunk_indexs[i];
+        yy_png_chunk_info *shared_chunk_info = info->chunks + shared_chunk_index;
+        
+        if (shared_chunk_index >= info->apng_shared_insert_index && !inserted) { // replace IDAT with fdAT
+            inserted = true;
+            for (uint32_t c = 0; c < frame_info->chunk_num; c++) {
+                yy_png_chunk_info *insert_chunk_info = info->chunks + frame_info->chunk_index + c;
+                if (insert_chunk_info->fourcc == YY_FOUR_CC('f', 'd', 'A', 'T')) {
+                    *((uint32_t *)(frame_data + data_offset)) = yy_swap_endian_uint32(insert_chunk_info->length - 4);
+                    *((uint32_t *)(frame_data + data_offset + 4)) = YY_FOUR_CC('I', 'D', 'A', 'T');
+                    memcpy(frame_data + data_offset + 8, data + insert_chunk_info->offset + 12, insert_chunk_info->length - 4);
+                    uint32_t crc = (uint32_t)crc32(0, frame_data + data_offset + 4, insert_chunk_info->length);
+                    *((uint32_t *)(frame_data + data_offset + insert_chunk_info->length + 4)) = yy_swap_endian_uint32(crc);
+                    data_offset += insert_chunk_info->length + 8;
+                } else { // IDAT
+                    memcpy(frame_data + data_offset, data + insert_chunk_info->offset, insert_chunk_info->length + 12);
+                    data_offset += insert_chunk_info->length + 12;
+                }
+            }
+        }
+        
+        if (shared_chunk_info->fourcc == YY_FOUR_CC('I', 'H', 'D', 'R')) {
+            uint8_t tmp[25] = {0};
+            memcpy(tmp, data + shared_chunk_info->offset, 25);
+            yy_png_chunk_IHDR IHDR = info->header;
+            IHDR.width = frame_info->frame_control.width;
+            IHDR.height = frame_info->frame_control.height;
+            yy_png_chunk_IHDR_write(&IHDR, tmp + 8);
+            *((uint32_t *)(tmp + 21)) = yy_swap_endian_uint32((uint32_t)crc32(0, tmp + 4, 17));
+            memcpy(frame_data + data_offset, tmp, 25);
+            data_offset += 25;
+        } else {
+            memcpy(frame_data + data_offset, data + shared_chunk_info->offset, shared_chunk_info->length + 12);
+            data_offset += shared_chunk_info->length + 12;
+        }
+    }
+    return frame_data;
+}
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+#pragma mark - Helper
+
+/// Returns byte-aligned size.
+static inline size_t YYImageByteAlign(size_t size, size_t alignment) {
+    return ((size + (alignment - 1)) / alignment) * alignment;
+}
+
+/// Convert degree to radians
+static inline CGFloat YYImageDegreesToRadians(CGFloat degrees) {
+    return degrees * M_PI / 180;
+}
+
+CGColorSpaceRef YYCGColorSpaceGetDeviceRGB() {
+    static CGColorSpaceRef space;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        space = CGColorSpaceCreateDeviceRGB();
+    });
+    return space;
+}
+
+CGColorSpaceRef YYCGColorSpaceGetDeviceGray() {
+    static CGColorSpaceRef space;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        space = CGColorSpaceCreateDeviceGray();
+    });
+    return space;
+}
+
+BOOL YYCGColorSpaceIsDeviceRGB(CGColorSpaceRef space) {
+    return space && CFEqual(space, YYCGColorSpaceGetDeviceRGB());
+}
+
+BOOL YYCGColorSpaceIsDeviceGray(CGColorSpaceRef space) {
+    return space && CFEqual(space, YYCGColorSpaceGetDeviceGray());
+}
+
+/**
+ A callback used in CGDataProviderCreateWithData() to release data.
+ 
+ Example:
+ 
+ void *data = malloc(size);
+ CGDataProviderRef provider = CGDataProviderCreateWithData(data, data, size, YYCGDataProviderReleaseDataCallback);
+ */
+static void YYCGDataProviderReleaseDataCallback(void *info, const void *data, size_t size) {
+    if (info) free(info);
+}
+
+/**
+ Decode an image to bitmap buffer with the specified format.
+ 
+ @param srcImage   Source image.
+ @param dest       Destination buffer. It should be zero before call this method.
+                   If decode succeed, you should release the dest->data using free().
+ @param destFormat Destination bitmap format.
+ 
+ @return Whether succeed.
+ 
+ @warning This method support iOS7.0 and later. If call it on iOS6, it just returns NO.
+ CG_AVAILABLE_STARTING(__MAC_10_9, __IPHONE_7_0)
+ */
+static BOOL YYCGImageDecodeToBitmapBufferWithAnyFormat(CGImageRef srcImage, vImage_Buffer *dest, vImage_CGImageFormat *destFormat) {
+    if (!srcImage || (((long)vImageConvert_AnyToAny) + 1 == 1) || !destFormat || !dest) return NO;
+    size_t width = CGImageGetWidth(srcImage);
+    size_t height = CGImageGetHeight(srcImage);
+    if (width == 0 || height == 0) return NO;
+    dest->data = NULL;
+    
+    vImage_Error error = kvImageNoError;
+    CFDataRef srcData = NULL;
+    vImageConverterRef convertor = NULL;
+    vImage_CGImageFormat srcFormat = {0};
+    srcFormat.bitsPerComponent = (uint32_t)CGImageGetBitsPerComponent(srcImage);
+    srcFormat.bitsPerPixel = (uint32_t)CGImageGetBitsPerPixel(srcImage);
+    srcFormat.colorSpace = CGImageGetColorSpace(srcImage);
+    srcFormat.bitmapInfo = CGImageGetBitmapInfo(srcImage) | CGImageGetAlphaInfo(srcImage);
+    
+    convertor = vImageConverter_CreateWithCGImageFormat(&srcFormat, destFormat, NULL, kvImageNoFlags, NULL);
+    if (!convertor) goto fail;
+    
+    CGDataProviderRef srcProvider = CGImageGetDataProvider(srcImage);
+    srcData = srcProvider ? CGDataProviderCopyData(srcProvider) : NULL; // decode
+    size_t srcLength = srcData ? CFDataGetLength(srcData) : 0;
+    const void *srcBytes = srcData ? CFDataGetBytePtr(srcData) : NULL;
+    if (srcLength == 0 || !srcBytes) goto fail;
+    
+    vImage_Buffer src = {0};
+    src.data = (void *)srcBytes;
+    src.width = width;
+    src.height = height;
+    src.rowBytes = CGImageGetBytesPerRow(srcImage);
+    
+    error = vImageBuffer_Init(dest, height, width, 32, kvImageNoFlags);
+    if (error != kvImageNoError) goto fail;
+    
+    error = vImageConvert_AnyToAny(convertor, &src, dest, NULL, kvImageNoFlags); // convert
+    if (error != kvImageNoError) goto fail;
+    
+    CFRelease(convertor);
+    CFRelease(srcData);
+    return YES;
+    
+fail:
+    if (convertor) CFRelease(convertor);
+    if (srcData) CFRelease(srcData);
+    if (dest->data) free(dest->data);
+    dest->data = NULL;
+    return NO;
+}
+
+/**
+ Decode an image to bitmap buffer with the 32bit format (such as ARGB8888).
+ 
+ @param srcImage   Source image.
+ @param dest       Destination buffer. It should be zero before call this method.
+                   If decode succeed, you should release the dest->data using free().
+ @param bitmapInfo Destination bitmap format.
+ 
+ @return Whether succeed.
+ */
+static BOOL YYCGImageDecodeToBitmapBufferWith32BitFormat(CGImageRef srcImage, vImage_Buffer *dest, CGBitmapInfo bitmapInfo) {
+    if (!srcImage || !dest) return NO;
+    size_t width = CGImageGetWidth(srcImage);
+    size_t height = CGImageGetHeight(srcImage);
+    if (width == 0 || height == 0) return NO;
+    
+    BOOL hasAlpha = NO;
+    BOOL alphaFirst = NO;
+    BOOL alphaPremultiplied = NO;
+    BOOL byteOrderNormal = NO;
+    
+    switch (bitmapInfo & kCGBitmapAlphaInfoMask) {
+        case kCGImageAlphaPremultipliedLast: {
+            hasAlpha = YES;
+            alphaPremultiplied = YES;
+        } break;
+        case kCGImageAlphaPremultipliedFirst: {
+            hasAlpha = YES;
+            alphaPremultiplied = YES;
+            alphaFirst = YES;
+        } break;
+        case kCGImageAlphaLast: {
+            hasAlpha = YES;
+        } break;
+        case kCGImageAlphaFirst: {
+            hasAlpha = YES;
+            alphaFirst = YES;
+        } break;
+        case kCGImageAlphaNoneSkipLast: {
+        } break;
+        case kCGImageAlphaNoneSkipFirst: {
+            alphaFirst = YES;
+        } break;
+        default: {
+            return NO;
+        } break;
+    }
+    
+    switch (bitmapInfo & kCGBitmapByteOrderMask) {
+        case kCGBitmapByteOrderDefault: {
+            byteOrderNormal = YES;
+        } break;
+        case kCGBitmapByteOrder32Little: {
+        } break;
+        case kCGBitmapByteOrder32Big: {
+            byteOrderNormal = YES;
+        } break;
+        default: {
+            return NO;
+        } break;
+    }
+    
+    /*
+     Try convert with vImageConvert_AnyToAny() (avaliable since iOS 7.0).
+     If fail, try decode with CGContextDrawImage().
+     CGBitmapContext use a premultiplied alpha format, unpremultiply may lose precision.
+     */
+    vImage_CGImageFormat destFormat = {0};
+    destFormat.bitsPerComponent = 8;
+    destFormat.bitsPerPixel = 32;
+    destFormat.colorSpace = YYCGColorSpaceGetDeviceRGB();
+    destFormat.bitmapInfo = bitmapInfo;
+    dest->data = NULL;
+    if (YYCGImageDecodeToBitmapBufferWithAnyFormat(srcImage, dest, &destFormat)) return YES;
+    
+    CGBitmapInfo contextBitmapInfo = bitmapInfo & kCGBitmapByteOrderMask;
+    if (!hasAlpha || alphaPremultiplied) {
+        contextBitmapInfo |= (bitmapInfo & kCGBitmapAlphaInfoMask);
+    } else {
+        contextBitmapInfo |= alphaFirst ? kCGImageAlphaPremultipliedFirst : kCGImageAlphaPremultipliedLast;
+    }
+    CGContextRef context = CGBitmapContextCreate(NULL, width, height, 8, 0, YYCGColorSpaceGetDeviceRGB(), contextBitmapInfo);
+    if (!context) goto fail;
+    
+    CGContextDrawImage(context, CGRectMake(0, 0, width, height), srcImage); // decode and convert
+    size_t bytesPerRow = CGBitmapContextGetBytesPerRow(context);
+    size_t length = height * bytesPerRow;
+    void *data = CGBitmapContextGetData(context);
+    if (length == 0 || !data) goto fail;
+    
+    dest->data = malloc(length);
+    dest->width = width;
+    dest->height = height;
+    dest->rowBytes = bytesPerRow;
+    if (!dest->data) goto fail;
+    
+    if (hasAlpha && !alphaPremultiplied) {
+        vImage_Buffer tmpSrc = {0};
+        tmpSrc.data = data;
+        tmpSrc.width = width;
+        tmpSrc.height = height;
+        tmpSrc.rowBytes = bytesPerRow;
+        vImage_Error error;
+        if (alphaFirst && byteOrderNormal) {
+            error = vImageUnpremultiplyData_ARGB8888(&tmpSrc, dest, kvImageNoFlags);
+        } else {
+            error = vImageUnpremultiplyData_RGBA8888(&tmpSrc, dest, kvImageNoFlags);
+        }
+        if (error != kvImageNoError) goto fail;
+    } else {
+        memcpy(dest->data, data, length);
+    }
+    
+    CFRelease(context);
+    return YES;
+    
+fail:
+    if (context) CFRelease(context);
+    if (dest->data) free(dest->data);
+    dest->data = NULL;
+    return NO;
+    return NO;
+}
+
+CGImageRef YYCGImageCreateDecodedCopy(CGImageRef imageRef, BOOL decodeForDisplay) {
+    if (!imageRef) return NULL;
+    size_t width = CGImageGetWidth(imageRef);
+    size_t height = CGImageGetHeight(imageRef);
+    if (width == 0 || height == 0) return NULL;
+    
+    if (decodeForDisplay) { //decode with redraw (may lose some precision)
+        CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo(imageRef) & kCGBitmapAlphaInfoMask;
+        BOOL hasAlpha = NO;
+        if (alphaInfo == kCGImageAlphaPremultipliedLast ||
+            alphaInfo == kCGImageAlphaPremultipliedFirst ||
+            alphaInfo == kCGImageAlphaLast ||
+            alphaInfo == kCGImageAlphaFirst) {
+            hasAlpha = YES;
+        }
+        // BGRA8888 (premultiplied) or BGRX8888
+        // same as UIGraphicsBeginImageContext() and -[UIView drawRect:]
+        CGBitmapInfo bitmapInfo = kCGBitmapByteOrder32Host;
+        bitmapInfo |= hasAlpha ? kCGImageAlphaPremultipliedFirst : kCGImageAlphaNoneSkipFirst;
+        CGContextRef context = CGBitmapContextCreate(NULL, width, height, 8, 0, YYCGColorSpaceGetDeviceRGB(), bitmapInfo);
+        if (!context) return NULL;
+        CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef); // decode
+        CGImageRef newImage = CGBitmapContextCreateImage(context);
+        CFRelease(context);
+        return newImage;
+        
+    } else {
+        CGColorSpaceRef space = CGImageGetColorSpace(imageRef);
+        size_t bitsPerComponent = CGImageGetBitsPerComponent(imageRef);
+        size_t bitsPerPixel = CGImageGetBitsPerPixel(imageRef);
+        size_t bytesPerRow = CGImageGetBytesPerRow(imageRef);
+        CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
+        if (bytesPerRow == 0 || width == 0 || height == 0) return NULL;
+        
+        CGDataProviderRef dataProvider = CGImageGetDataProvider(imageRef);
+        if (!dataProvider) return NULL;
+        CFDataRef data = CGDataProviderCopyData(dataProvider); // decode
+        if (!data) return NULL;
+        
+        CGDataProviderRef newProvider = CGDataProviderCreateWithCFData(data);
+        CFRelease(data);
+        if (!newProvider) return NULL;
+        
+        CGImageRef newImage = CGImageCreate(width, height, bitsPerComponent, bitsPerPixel, bytesPerRow, space, bitmapInfo, newProvider, NULL, false, kCGRenderingIntentDefault);
+        CFRelease(newProvider);
+        return newImage;
+    }
+}
+
+CGImageRef YYCGImageCreateAffineTransformCopy(CGImageRef imageRef, CGAffineTransform transform, CGSize destSize, CGBitmapInfo destBitmapInfo) {
+    if (!imageRef) return NULL;
+    size_t srcWidth = CGImageGetWidth(imageRef);
+    size_t srcHeight = CGImageGetHeight(imageRef);
+    size_t destWidth = round(destSize.width);
+    size_t destHeight = round(destSize.height);
+    if (srcWidth == 0 || srcHeight == 0 || destWidth == 0 || destHeight == 0) return NULL;
+    
+    CGDataProviderRef tmpProvider = NULL, destProvider = NULL;
+    CGImageRef tmpImage = NULL, destImage = NULL;
+    vImage_Buffer src = {0}, tmp = {0}, dest = {0};
+    if(!YYCGImageDecodeToBitmapBufferWith32BitFormat(imageRef, &src, kCGImageAlphaFirst | kCGBitmapByteOrderDefault)) return NULL;
+    
+    size_t destBytesPerRow = YYImageByteAlign(destWidth * 4, 32);
+    tmp.data = malloc(destHeight * destBytesPerRow);
+    if (!tmp.data) goto fail;
+    
+    tmp.width = destWidth;
+    tmp.height = destHeight;
+    tmp.rowBytes = destBytesPerRow;
+    vImage_CGAffineTransform vTransform = *((vImage_CGAffineTransform *)&transform);
+    uint8_t backColor[4] = {0};
+    vImage_Error error = vImageAffineWarpCG_ARGB8888(&src, &tmp, NULL, &vTransform, backColor, kvImageBackgroundColorFill);
+    if (error != kvImageNoError) goto fail;
+    free(src.data);
+    src.data = NULL;
+    
+    tmpProvider = CGDataProviderCreateWithData(tmp.data, tmp.data, destHeight * destBytesPerRow, YYCGDataProviderReleaseDataCallback);
+    if (!tmpProvider) goto fail;
+    tmp.data = NULL; // hold by provider
+    tmpImage = CGImageCreate(destWidth, destHeight, 8, 32, destBytesPerRow, YYCGColorSpaceGetDeviceRGB(), kCGImageAlphaFirst | kCGBitmapByteOrderDefault, tmpProvider, NULL, false, kCGRenderingIntentDefault);
+    if (!tmpImage) goto fail;
+    CFRelease(tmpProvider);
+    tmpProvider = NULL;
+    
+    if ((destBitmapInfo & kCGBitmapAlphaInfoMask) == kCGImageAlphaFirst &&
+        (destBitmapInfo & kCGBitmapByteOrderMask) != kCGBitmapByteOrder32Little) {
+        return tmpImage;
+    }
+    
+    if (!YYCGImageDecodeToBitmapBufferWith32BitFormat(tmpImage, &dest, destBitmapInfo)) goto fail;
+    CFRelease(tmpImage);
+    tmpImage = NULL;
+    
+    destProvider = CGDataProviderCreateWithData(dest.data, dest.data, destHeight * destBytesPerRow, YYCGDataProviderReleaseDataCallback);
+    if (!destProvider) goto fail;
+    dest.data = NULL; // hold by provider
+    destImage = CGImageCreate(destWidth, destHeight, 8, 32, destBytesPerRow, YYCGColorSpaceGetDeviceRGB(), destBitmapInfo, destProvider, NULL, false, kCGRenderingIntentDefault);
+    if (!destImage) goto fail;
+    CFRelease(destProvider);
+    destProvider = NULL;
+    
+    return destImage;
+    
+fail:
+    if (src.data) free(src.data);
+    if (tmp.data) free(tmp.data);
+    if (dest.data) free(dest.data);
+    if (tmpProvider) CFRelease(tmpProvider);
+    if (tmpImage) CFRelease(tmpImage);
+    if (destProvider) CFRelease(destProvider);
+    return NULL;
+}
+
+UIImageOrientation YYUIImageOrientationFromEXIFValue(NSInteger value) {
+    switch (value) {
+        case kCGImagePropertyOrientationUp: return UIImageOrientationUp;
+        case kCGImagePropertyOrientationDown: return UIImageOrientationDown;
+        case kCGImagePropertyOrientationLeft: return UIImageOrientationLeft;
+        case kCGImagePropertyOrientationRight: return UIImageOrientationRight;
+        case kCGImagePropertyOrientationUpMirrored: return UIImageOrientationUpMirrored;
+        case kCGImagePropertyOrientationDownMirrored: return UIImageOrientationDownMirrored;
+        case kCGImagePropertyOrientationLeftMirrored: return UIImageOrientationLeftMirrored;
+        case kCGImagePropertyOrientationRightMirrored: return UIImageOrientationRightMirrored;
+        default: return UIImageOrientationUp;
+    }
+}
+
+NSInteger YYUIImageOrientationToEXIFValue(UIImageOrientation orientation) {
+    switch (orientation) {
+        case UIImageOrientationUp: return kCGImagePropertyOrientationUp;
+        case UIImageOrientationDown: return kCGImagePropertyOrientationDown;
+        case UIImageOrientationLeft: return kCGImagePropertyOrientationLeft;
+        case UIImageOrientationRight: return kCGImagePropertyOrientationRight;
+        case UIImageOrientationUpMirrored: return kCGImagePropertyOrientationUpMirrored;
+        case UIImageOrientationDownMirrored: return kCGImagePropertyOrientationDownMirrored;
+        case UIImageOrientationLeftMirrored: return kCGImagePropertyOrientationLeftMirrored;
+        case UIImageOrientationRightMirrored: return kCGImagePropertyOrientationRightMirrored;
+        default: return kCGImagePropertyOrientationUp;
+    }
+}
+
+CGImageRef YYCGImageCreateCopyWithOrientation(CGImageRef imageRef, UIImageOrientation orientation, CGBitmapInfo destBitmapInfo) {
+    if (!imageRef) return NULL;
+    if (orientation == UIImageOrientationUp) return (CGImageRef)CFRetain(imageRef);
+    
+    size_t width = CGImageGetWidth(imageRef);
+    size_t height = CGImageGetHeight(imageRef);
+    
+    CGAffineTransform transform = CGAffineTransformIdentity;
+    BOOL swapWidthAndHeight = NO;
+    switch (orientation) {
+        case UIImageOrientationDown: {
+            transform = CGAffineTransformMakeRotation(YYImageDegreesToRadians(180));
+            transform = CGAffineTransformTranslate(transform, -(CGFloat)width, -(CGFloat)height);
+        } break;
+        case UIImageOrientationLeft: {
+            transform = CGAffineTransformMakeRotation(YYImageDegreesToRadians(90));
+            transform = CGAffineTransformTranslate(transform, -(CGFloat)0, -(CGFloat)height);
+            swapWidthAndHeight = YES;
+        } break;
+        case UIImageOrientationRight: {
+            transform = CGAffineTransformMakeRotation(YYImageDegreesToRadians(-90));
+            transform = CGAffineTransformTranslate(transform, -(CGFloat)width, (CGFloat)0);
+            swapWidthAndHeight = YES;
+        } break;
+        case UIImageOrientationUpMirrored: {
+            transform = CGAffineTransformTranslate(transform, (CGFloat)width, 0);
+            transform = CGAffineTransformScale(transform, -1, 1);
+        } break;
+        case UIImageOrientationDownMirrored: {
+            transform = CGAffineTransformTranslate(transform, 0, (CGFloat)height);
+            transform = CGAffineTransformScale(transform, 1, -1);
+        } break;
+        case UIImageOrientationLeftMirrored: {
+            transform = CGAffineTransformMakeRotation(YYImageDegreesToRadians(-90));
+            transform = CGAffineTransformScale(transform, 1, -1);
+            transform = CGAffineTransformTranslate(transform, -(CGFloat)width, -(CGFloat)height);
+            swapWidthAndHeight = YES;
+        } break;
+        case UIImageOrientationRightMirrored: {
+            transform = CGAffineTransformMakeRotation(YYImageDegreesToRadians(90));
+            transform = CGAffineTransformScale(transform, 1, -1);
+            swapWidthAndHeight = YES;
+        } break;
+        default: break;
+    }
+    if (CGAffineTransformIsIdentity(transform)) return (CGImageRef)CFRetain(imageRef);
+    
+    CGSize destSize = {width, height};
+    if (swapWidthAndHeight) {
+        destSize.width = height;
+        destSize.height = width;
+    }
+    
+    return YYCGImageCreateAffineTransformCopy(imageRef, transform, destSize, destBitmapInfo);
+}
+
+YYImageType YYImageDetectType(CFDataRef data) {
+    if (!data) return YYImageTypeUnknown;
+    uint64_t length = CFDataGetLength(data);
+    if (length < 16) return YYImageTypeUnknown;
+    
+    const char *bytes = (char *)CFDataGetBytePtr(data);
+    
+    uint32_t magic4 = *((uint32_t *)bytes);
+    switch (magic4) {
+        case YY_FOUR_CC(0x4D, 0x4D, 0x00, 0x2A): { // big endian TIFF
+            return YYImageTypeTIFF;
+        } break;
+            
+        case YY_FOUR_CC(0x49, 0x49, 0x2A, 0x00): { // little endian TIFF
+            return YYImageTypeTIFF;
+        } break;
+            
+        case YY_FOUR_CC(0x00, 0x00, 0x01, 0x00): { // ICO
+            return YYImageTypeICO;
+        } break;
+            
+        case YY_FOUR_CC(0x00, 0x00, 0x02, 0x00): { // CUR
+            return YYImageTypeICO;
+        } break;
+            
+        case YY_FOUR_CC('i', 'c', 'n', 's'): { // ICNS
+            return YYImageTypeICNS;
+        } break;
+            
+        case YY_FOUR_CC('G', 'I', 'F', '8'): { // GIF
+            return YYImageTypeGIF;
+        } break;
+            
+        case YY_FOUR_CC(0x89, 'P', 'N', 'G'): {  // PNG
+            uint32_t tmp = *((uint32_t *)(bytes + 4));
+            if (tmp == YY_FOUR_CC('\r', '\n', 0x1A, '\n')) {
+                return YYImageTypePNG;
+            }
+        } break;
+            
+        case YY_FOUR_CC('R', 'I', 'F', 'F'): { // WebP
+            uint32_t tmp = *((uint32_t *)(bytes + 8));
+            if (tmp == YY_FOUR_CC('W', 'E', 'B', 'P')) {
+                return YYImageTypeWebP;
+            }
+        } break;
+        /*
+        case YY_FOUR_CC('B', 'P', 'G', 0xFB): { // BPG
+            return YYImageTypeBPG;
+        } break;
+        */
+    }
+    
+    uint16_t magic2 = *((uint16_t *)bytes);
+    switch (magic2) {
+        case YY_TWO_CC('B', 'A'):
+        case YY_TWO_CC('B', 'M'):
+        case YY_TWO_CC('I', 'C'):
+        case YY_TWO_CC('P', 'I'):
+        case YY_TWO_CC('C', 'I'):
+        case YY_TWO_CC('C', 'P'): { // BMP
+            return YYImageTypeBMP;
+        }
+        case YY_TWO_CC(0xFF, 0x4F): { // JPEG2000
+            return YYImageTypeJPEG2000;
+        }
+    }
+    
+    // JPG             FF D8 FF
+    if (memcmp(bytes,"\377\330\377",3) == 0) return YYImageTypeJPEG;
+    
+    // JP2
+    if (memcmp(bytes + 4, "\152\120\040\040\015", 5) == 0) return YYImageTypeJPEG2000;
+    
+    return YYImageTypeUnknown;
+}
+
+CFStringRef YYImageTypeToUTType(YYImageType type) {
+    switch (type) {
+        case YYImageTypeJPEG: return kUTTypeJPEG;
+        case YYImageTypeJPEG2000: return kUTTypeJPEG2000;
+        case YYImageTypeTIFF: return kUTTypeTIFF;
+        case YYImageTypeBMP: return kUTTypeBMP;
+        case YYImageTypeICO: return kUTTypeICO;
+        case YYImageTypeICNS: return kUTTypeAppleICNS;
+        case YYImageTypeGIF: return kUTTypeGIF;
+        case YYImageTypePNG: return kUTTypePNG;
+        default: return NULL;
+    }
+}
+
+YYImageType YYImageTypeFromUTType(CFStringRef uti) {
+    static NSDictionary *dic;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        dic = @{(id)kUTTypeJPEG : @(YYImageTypeJPEG),
+                (id)kUTTypeJPEG2000 : @(YYImageTypeJPEG2000),
+                (id)kUTTypeTIFF : @(YYImageTypeTIFF),
+                (id)kUTTypeBMP : @(YYImageTypeBMP),
+                (id)kUTTypeICO : @(YYImageTypeICO),
+                (id)kUTTypeAppleICNS : @(YYImageTypeICNS),
+                (id)kUTTypeGIF : @(YYImageTypeGIF),
+                (id)kUTTypePNG : @(YYImageTypePNG)};
+    });
+    if (!uti) return YYImageTypeUnknown;
+    NSNumber *num = dic[(__bridge __strong id)(uti)];
+    return num.unsignedIntegerValue;
+}
+
+NSString *YYImageTypeGetExtension(YYImageType type) {
+    switch (type) {
+        case YYImageTypeJPEG: return @"jpg";
+        case YYImageTypeJPEG2000: return @"jp2";
+        case YYImageTypeTIFF: return @"tiff";
+        case YYImageTypeBMP: return @"bmp";
+        case YYImageTypeICO: return @"ico";
+        case YYImageTypeICNS: return @"icns";
+        case YYImageTypeGIF: return @"gif";
+        case YYImageTypePNG: return @"png";
+        case YYImageTypeWebP: return @"webp";
+        default: return nil;
+    }
+}
+
+CFDataRef YYCGImageCreateEncodedData(CGImageRef imageRef, YYImageType type, CGFloat quality) {
+    if (!imageRef) return nil;
+    quality = quality < 0 ? 0 : quality > 1 ? 1 : quality;
+    
+    if (type == YYImageTypeWebP) {
+#if YYIMAGE_WEBP_ENABLED
+        if (quality == 1) {
+            return YYCGImageCreateEncodedWebPData(imageRef, YES, quality, 4, YYImagePresetDefault);
+        } else {
+            return YYCGImageCreateEncodedWebPData(imageRef, NO, quality, 4, YYImagePresetDefault);
+        }
+#else
+        return NULL;
+#endif
+    }
+    
+    CFStringRef uti = YYImageTypeToUTType(type);
+    if (!uti) return nil;
+    
+    CFMutableDataRef data = CFDataCreateMutable(CFAllocatorGetDefault(), 0);
+    if (!data) return NULL;
+    CGImageDestinationRef dest = CGImageDestinationCreateWithData(data, uti, 1, NULL);
+    if (!dest) {
+        CFRelease(data);
+        return NULL;
+    }
+    NSDictionary *options = @{(id)kCGImageDestinationLossyCompressionQuality : @(quality) };
+    CGImageDestinationAddImage(dest, imageRef, (CFDictionaryRef)options);
+    if (!CGImageDestinationFinalize(dest)) {
+        CFRelease(data);
+        CFRelease(dest);
+        return nil;
+    }
+    CFRelease(dest);
+    
+    if (CFDataGetLength(data) == 0) {
+        CFRelease(data);
+        return NULL;
+    }
+    return data;
+}
+
+#if YYIMAGE_WEBP_ENABLED
+
+BOOL YYImageWebPAvailable() {
+    return YES;
+}
+
+CFDataRef YYCGImageCreateEncodedWebPData(CGImageRef imageRef, BOOL lossless, CGFloat quality, int compressLevel, YYImagePreset preset) {
+    if (!imageRef) return nil;
+    size_t width = CGImageGetWidth(imageRef);
+    size_t height = CGImageGetHeight(imageRef);
+    if (width == 0 || width > WEBP_MAX_DIMENSION) return nil;
+    if (height == 0 || height > WEBP_MAX_DIMENSION) return nil;
+    
+    vImage_Buffer buffer = {0};
+    if(!YYCGImageDecodeToBitmapBufferWith32BitFormat(imageRef, &buffer, kCGImageAlphaLast | kCGBitmapByteOrderDefault)) return nil;
+    
+    WebPConfig config = {0};
+    WebPPicture picture = {0};
+    WebPMemoryWriter writer = {0};
+    CFDataRef webpData = NULL;
+    BOOL pictureNeedFree = NO;
+    
+    quality = quality < 0 ? 0 : quality > 1 ? 1 : quality;
+    preset = preset > YYImagePresetText ? YYImagePresetDefault : preset;
+    compressLevel = compressLevel < 0 ? 0 : compressLevel > 6 ? 6 : compressLevel;
+    if (!WebPConfigPreset(&config, (WebPPreset)preset, quality)) goto fail;
+    
+    config.quality = round(quality * 100.0);
+    config.lossless = lossless;
+    config.method = compressLevel;
+    switch ((WebPPreset)preset) {
+        case WEBP_PRESET_DEFAULT: {
+            config.image_hint = WEBP_HINT_DEFAULT;
+        } break;
+        case WEBP_PRESET_PICTURE: {
+            config.image_hint = WEBP_HINT_PICTURE;
+        } break;
+        case WEBP_PRESET_PHOTO: {
+            config.image_hint = WEBP_HINT_PHOTO;
+        } break;
+        case WEBP_PRESET_DRAWING:
+        case WEBP_PRESET_ICON:
+        case WEBP_PRESET_TEXT: {
+            config.image_hint = WEBP_HINT_GRAPH;
+        } break;
+    }
+    if (!WebPValidateConfig(&config)) goto fail;
+    
+    if (!WebPPictureInit(&picture)) goto fail;
+    pictureNeedFree = YES;
+    picture.width = (int)buffer.width;
+    picture.height = (int)buffer.height;
+    picture.use_argb = lossless;
+    if(!WebPPictureImportRGBA(&picture, buffer.data, (int)buffer.rowBytes)) goto fail;
+    
+    WebPMemoryWriterInit(&writer);
+    picture.writer = WebPMemoryWrite;
+    picture.custom_ptr = &writer;
+    if(!WebPEncode(&config, &picture)) goto fail;
+    
+    webpData = CFDataCreate(CFAllocatorGetDefault(), writer.mem, writer.size);
+    free(writer.mem);
+    WebPPictureFree(&picture);
+    free(buffer.data);
+    return webpData;
+    
+fail:
+    if (buffer.data) free(buffer.data);
+    if (pictureNeedFree) WebPPictureFree(&picture);
+    return nil;
+}
+
+NSUInteger YYImageGetWebPFrameCount(CFDataRef webpData) {
+    if (!webpData || CFDataGetLength(webpData) == 0) return 0;
+    
+    WebPData data = {CFDataGetBytePtr(webpData), CFDataGetLength(webpData)};
+    WebPDemuxer *demuxer = WebPDemux(&data);
+    if (!demuxer) return 0;
+    NSUInteger webpFrameCount = WebPDemuxGetI(demuxer, WEBP_FF_FRAME_COUNT);
+    WebPDemuxDelete(demuxer);
+    return webpFrameCount;
+}
+
+CGImageRef YYCGImageCreateWithWebPData(CFDataRef webpData,
+                                       BOOL decodeForDisplay,
+                                       BOOL useThreads,
+                                       BOOL bypassFiltering,
+                                       BOOL noFancyUpsampling) {
+    /*
+     Call WebPDecode() on a multi-frame webp data will get an error (VP8_STATUS_UNSUPPORTED_FEATURE).
+     Use WebPDemuxer to unpack it first.
+     */
+    WebPData data = {0};
+    WebPDemuxer *demuxer = NULL;
+    
+    int frameCount = 0, canvasWidth = 0, canvasHeight = 0;
+    WebPIterator iter = {0};
+    BOOL iterInited = NO;
+    const uint8_t *payload = NULL;
+    size_t payloadSize = 0;
+    WebPDecoderConfig config = {0};
+    
+    BOOL hasAlpha = NO;
+    size_t bitsPerComponent = 0, bitsPerPixel = 0, bytesPerRow = 0, destLength = 0;
+    CGBitmapInfo bitmapInfo = 0;
+    WEBP_CSP_MODE colorspace = 0;
+    void *destBytes = NULL;
+    CGDataProviderRef provider = NULL;
+    CGImageRef imageRef = NULL;
+    
+    if (!webpData || CFDataGetLength(webpData) == 0) return NULL;
+    data.bytes = CFDataGetBytePtr(webpData);
+    data.size = CFDataGetLength(webpData);
+    demuxer = WebPDemux(&data);
+    if (!demuxer) goto fail;
+    
+    frameCount = WebPDemuxGetI(demuxer, WEBP_FF_FRAME_COUNT);
+    if (frameCount == 0) {
+        goto fail;
+        
+    } else if (frameCount == 1) { // single-frame
+        payload = data.bytes;
+        payloadSize = data.size;
+        if (!WebPInitDecoderConfig(&config)) goto fail;
+        if (WebPGetFeatures(payload , payloadSize, &config.input) != VP8_STATUS_OK) goto fail;
+        canvasWidth = config.input.width;
+        canvasHeight = config.input.height;
+        
+    } else { // multi-frame
+        canvasWidth = WebPDemuxGetI(demuxer, WEBP_FF_CANVAS_WIDTH);
+        canvasHeight = WebPDemuxGetI(demuxer, WEBP_FF_CANVAS_HEIGHT);
+        if (canvasWidth < 1 || canvasHeight < 1) goto fail;
+        
+        if (!WebPDemuxGetFrame(demuxer, 1, &iter)) goto fail;
+        iterInited = YES;
+        
+        if (iter.width > canvasWidth || iter.height > canvasHeight) goto fail;
+        payload = iter.fragment.bytes;
+        payloadSize = iter.fragment.size;
+        
+        if (!WebPInitDecoderConfig(&config)) goto fail;
+        if (WebPGetFeatures(payload , payloadSize, &config.input) != VP8_STATUS_OK) goto fail;
+    }
+    if (payload == NULL || payloadSize == 0) goto fail;
+    
+    hasAlpha = config.input.has_alpha;
+    bitsPerComponent = 8;
+    bitsPerPixel = 32;
+    bytesPerRow = YYImageByteAlign(bitsPerPixel / 8 * canvasWidth, 32);
+    destLength = bytesPerRow * canvasHeight;
+    if (decodeForDisplay) {
+        bitmapInfo = kCGBitmapByteOrder32Host;
+        bitmapInfo |= hasAlpha ? kCGImageAlphaPremultipliedFirst : kCGImageAlphaNoneSkipFirst;
+        colorspace = MODE_bgrA; // small endian
+    } else {
+        bitmapInfo = kCGBitmapByteOrderDefault;
+        bitmapInfo |= hasAlpha ? kCGImageAlphaLast : kCGImageAlphaNoneSkipLast;
+        colorspace = MODE_RGBA;
+    }
+    destBytes = calloc(1, destLength);
+    if (!destBytes) goto fail;
+    
+    config.options.use_threads = useThreads; //speed up 23%
+    config.options.bypass_filtering = bypassFiltering; //speed up 11%, cause some banding
+    config.options.no_fancy_upsampling = noFancyUpsampling; //speed down 16%, lose some details
+    config.output.colorspace = colorspace;
+    config.output.is_external_memory = 1;
+    config.output.u.RGBA.rgba = destBytes;
+    config.output.u.RGBA.stride = (int)bytesPerRow;
+    config.output.u.RGBA.size = destLength;
+    
+    VP8StatusCode result = WebPDecode(payload, payloadSize, &config);
+    if ((result != VP8_STATUS_OK) && (result != VP8_STATUS_NOT_ENOUGH_DATA)) goto fail;
+    
+    if (iter.x_offset != 0 || iter.y_offset != 0) {
+        void *tmp = calloc(1, destLength);
+        if (tmp) {
+            vImage_Buffer src = {destBytes, canvasHeight, canvasWidth, bytesPerRow};
+            vImage_Buffer dest = {tmp, canvasHeight, canvasWidth, bytesPerRow};
+            vImage_CGAffineTransform transform = {1, 0, 0, 1, iter.x_offset, -iter.y_offset};
+            uint8_t backColor[4] = {0};
+            vImageAffineWarpCG_ARGB8888(&src, &dest, NULL, &transform, backColor, kvImageBackgroundColorFill);
+            memcpy(destBytes, tmp, destLength);
+            free(tmp);
+        }
+    }
+    
+    provider = CGDataProviderCreateWithData(destBytes, destBytes, destLength, YYCGDataProviderReleaseDataCallback);
+    if (!provider) goto fail;
+    destBytes = NULL; // hold by provider
+    
+    imageRef = CGImageCreate(canvasWidth, canvasHeight, bitsPerComponent, bitsPerPixel, bytesPerRow, YYCGColorSpaceGetDeviceRGB(), bitmapInfo, provider, NULL, false, kCGRenderingIntentDefault);
+    
+    CFRelease(provider);
+    if (iterInited) WebPDemuxReleaseIterator(&iter);
+    WebPDemuxDelete(demuxer);
+    
+    return imageRef;
+    
+fail:
+    if (destBytes) free(destBytes);
+    if (provider) CFRelease(provider);
+    if (iterInited) WebPDemuxReleaseIterator(&iter);
+    if (demuxer) WebPDemuxDelete(demuxer);
+    return NULL;
+}
+
+#else
+
+BOOL YYImageWebPAvailable() {
+    return NO;
+}
+
+CFDataRef YYCGImageCreateEncodedWebPData(CGImageRef imageRef, BOOL lossless, CGFloat quality, int compressLevel, YYImagePreset preset) {
+    NSLog(@"WebP decoder is disabled");
+    return NULL;
+}
+
+NSUInteger YYImageGetWebPFrameCount(CFDataRef webpData) {
+    NSLog(@"WebP decoder is disabled");
+    return 0;
+}
+
+CGImageRef YYCGImageCreateWithWebPData(CFDataRef webpData,
+                                       BOOL decodeForDisplay,
+                                       BOOL useThreads,
+                                       BOOL bypassFiltering,
+                                       BOOL noFancyUpsampling) {
+    NSLog(@"WebP decoder is disabled");
+    return NULL;
+}
+
+#endif
+
+
+////////////////////////////////////////////////////////////////////////////////
+#pragma mark - Decoder
+
+@implementation YYImageFrame
++ (instancetype)frameWithImage:(UIImage *)image {
+    YYImageFrame *frame = [self new];
+    frame.image = image;
+    return frame;
+}
+- (id)copyWithZone:(NSZone *)zone {
+    YYImageFrame *frame = [self.class new];
+    frame.index = _index;
+    frame.width = _width;
+    frame.height = _height;
+    frame.offsetX = _offsetX;
+    frame.offsetY = _offsetY;
+    frame.duration = _duration;
+    frame.dispose = _dispose;
+    frame.blend = _blend;
+    frame.image = _image.copy;
+    return frame;
+}
+@end
+
+// Internal frame object.
+@interface _YYImageDecoderFrame : YYImageFrame
+@property (nonatomic, assign) BOOL hasAlpha;                ///< Whether frame has alpha.
+@property (nonatomic, assign) BOOL isFullSize;              ///< Whether frame fill the canvas.
+@property (nonatomic, assign) NSUInteger blendFromIndex;    ///< Blend from frame index to current frame.
+@end
+
+@implementation _YYImageDecoderFrame
+- (id)copyWithZone:(NSZone *)zone {
+    _YYImageDecoderFrame *frame = [super copyWithZone:zone];
+    frame.hasAlpha = _hasAlpha;
+    frame.isFullSize = _isFullSize;
+    frame.blendFromIndex = _blendFromIndex;
+    return frame;
+}
+@end
+
+
+@implementation YYImageDecoder {
+    pthread_mutex_t _lock; // recursive lock
+    
+    BOOL _sourceTypeDetected;
+    CGImageSourceRef _source;
+    yy_png_info *_apngSource;
+#if YYIMAGE_WEBP_ENABLED
+    WebPDemuxer *_webpSource;
+#endif
+    
+    UIImageOrientation _orientation;
+    dispatch_semaphore_t _framesLock;
+    NSArray *_frames; ///< Array<GGImageDecoderFrame>, without image
+    BOOL _needBlend;
+    NSUInteger _blendFrameIndex;
+    CGContextRef _blendCanvas;
+}
+
+- (void)dealloc {
+    if (_source) CFRelease(_source);
+    if (_apngSource) yy_png_info_release(_apngSource);
+#if YYIMAGE_WEBP_ENABLED
+    if (_webpSource) WebPDemuxDelete(_webpSource);
+#endif
+    if (_blendCanvas) CFRelease(_blendCanvas);
+    pthread_mutex_destroy(&_lock);
+}
+
++ (instancetype)decoderWithData:(NSData *)data scale:(CGFloat)scale {
+    if (!data) return nil;
+    YYImageDecoder *decoder = [[YYImageDecoder alloc] initWithScale:scale];
+    [decoder updateData:data final:YES];
+    if (decoder.frameCount == 0) return nil;
+    return decoder;
+}
+
+- (instancetype)init {
+    return [self initWithScale:[UIScreen mainScreen].scale];
+}
+
+- (instancetype)initWithScale:(CGFloat)scale {
+    self = [super init];
+    if (scale <= 0) scale = 1;
+    _scale = scale;
+    _framesLock = dispatch_semaphore_create(1);
+    
+    pthread_mutexattr_t attr;
+    pthread_mutexattr_init (&attr);
+    pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_RECURSIVE);
+    pthread_mutex_init (&_lock, &attr);
+    pthread_mutexattr_destroy (&attr);
+    
+    return self;
+}
+
+- (BOOL)updateData:(NSData *)data final:(BOOL)final {
+    BOOL result = NO;
+    pthread_mutex_lock(&_lock);
+    result = [self _updateData:data final:final];
+    pthread_mutex_unlock(&_lock);
+    return result;
+}
+
+- (YYImageFrame *)frameAtIndex:(NSUInteger)index decodeForDisplay:(BOOL)decodeForDisplay {
+    YYImageFrame *result = nil;
+    pthread_mutex_lock(&_lock);
+    result = [self _frameAtIndex:index decodeForDisplay:decodeForDisplay];
+    pthread_mutex_unlock(&_lock);
+    return result;
+}
+
+- (NSTimeInterval)frameDurationAtIndex:(NSUInteger)index {
+    NSTimeInterval result = 0;
+    dispatch_semaphore_wait(_framesLock, DISPATCH_TIME_FOREVER);
+    if (index < _frames.count) {
+        result = ((_YYImageDecoderFrame *)_frames[index]).duration;
+    }
+    dispatch_semaphore_signal(_framesLock);
+    return result;
+}
+
+- (NSDictionary *)framePropertiesAtIndex:(NSUInteger)index {
+    NSDictionary *result = nil;
+    pthread_mutex_lock(&_lock);
+    result = [self _framePropertiesAtIndex:index];
+    pthread_mutex_unlock(&_lock);
+    return result;
+}
+
+- (NSDictionary *)imageProperties {
+    NSDictionary *result = nil;
+    pthread_mutex_lock(&_lock);
+    result = [self _imageProperties];
+    pthread_mutex_unlock(&_lock);
+    return result;
+}
+
+#pragma private (wrap)
+
+- (BOOL)_updateData:(NSData *)data final:(BOOL)final {
+    if (_finalized) return NO;
+    if (data.length < _data.length) return NO;
+    _finalized = final;
+    _data = data;
+    
+    YYImageType type = YYImageDetectType((__bridge CFDataRef)data);
+    if (_sourceTypeDetected) {
+        if (_type != type) {
+            return NO;
+        } else {
+            [self _updateSource];
+        }
+    } else {
+        if (_data.length > 16) {
+            _type = type;
+            _sourceTypeDetected = YES;
+            [self _updateSource];
+        }
+    }
+    return YES;
+}
+
+- (YYImageFrame *)_frameAtIndex:(NSUInteger)index decodeForDisplay:(BOOL)decodeForDisplay {
+    if (index >= _frames.count) return 0;
+    _YYImageDecoderFrame *frame = [(_YYImageDecoderFrame *)_frames[index] copy];
+    BOOL decoded = NO;
+    BOOL extendToCanvas = NO;
+    if (_type != YYImageTypeICO && decodeForDisplay) { // ICO contains multi-size frame and should not extend to canvas.
+        extendToCanvas = YES;
+    }
+    
+    if (!_needBlend) {
+        CGImageRef imageRef = [self _newUnblendedImageAtIndex:index extendToCanvas:extendToCanvas decoded:&decoded];
+        if (!imageRef) return nil;
+        if (decodeForDisplay && !decoded) {
+            CGImageRef imageRefDecoded = YYCGImageCreateDecodedCopy(imageRef, YES);
+            if (imageRefDecoded) {
+                CFRelease(imageRef);
+                imageRef = imageRefDecoded;
+                decoded = YES;
+            }
+        }
+        UIImage *image = [UIImage imageWithCGImage:imageRef scale:_scale orientation:_orientation];
+        CFRelease(imageRef);
+        if (!image) return nil;
+        image.yy_isDecodedForDisplay = decoded;
+        frame.image = image;
+        return frame;
+    }
+    
+    // blend
+    if (![self _createBlendContextIfNeeded]) return nil;
+    CGImageRef imageRef = NULL;
+    
+    if (_blendFrameIndex + 1 == frame.index) {
+        imageRef = [self _newBlendedImageWithFrame:frame];
+        _blendFrameIndex = index;
+    } else { // should draw canvas from previous frame
+        _blendFrameIndex = NSNotFound;
+        CGContextClearRect(_blendCanvas, CGRectMake(0, 0, _width, _height));
+        
+        if (frame.blendFromIndex == frame.index) {
+            CGImageRef unblendedImage = [self _newUnblendedImageAtIndex:index extendToCanvas:NO decoded:NULL];
+            if (unblendedImage) {
+                CGContextDrawImage(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height), unblendedImage);
+                CFRelease(unblendedImage);
+            }
+            imageRef = CGBitmapContextCreateImage(_blendCanvas);
+            if (frame.dispose == YYImageDisposeBackground) {
+                CGContextClearRect(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height));
+            }
+            _blendFrameIndex = index;
+        } else { // canvas is not ready
+            for (uint32_t i = (uint32_t)frame.blendFromIndex; i <= (uint32_t)frame.index; i++) {
+                if (i == frame.index) {
+                    if (!imageRef) imageRef = [self _newBlendedImageWithFrame:frame];
+                } else {
+                    [self _blendImageWithFrame:_frames[i]];
+                }
+            }
+            _blendFrameIndex = index;
+        }
+    }
+    
+    if (!imageRef) return nil;
+    UIImage *image = [UIImage imageWithCGImage:imageRef scale:_scale orientation:_orientation];
+    CFRelease(imageRef);
+    if (!image) return nil;
+    
+    image.yy_isDecodedForDisplay = YES;
+    frame.image = image;
+    if (extendToCanvas) {
+        frame.width = _width;
+        frame.height = _height;
+        frame.offsetX = 0;
+        frame.offsetY = 0;
+        frame.dispose = YYImageDisposeNone;
+        frame.blend = YYImageBlendNone;
+    }
+    return frame;
+}
+
+- (NSDictionary *)_framePropertiesAtIndex:(NSUInteger)index {
+    if (index >= _frames.count) return nil;
+    if (!_source) return nil;
+    CFDictionaryRef properties = CGImageSourceCopyPropertiesAtIndex(_source, index, NULL);
+    if (!properties) return nil;
+    return CFBridgingRelease(properties);
+}
+
+- (NSDictionary *)_imageProperties {
+    if (!_source) return nil;
+    CFDictionaryRef properties = CGImageSourceCopyProperties(_source, NULL);
+    if (!properties) return nil;
+    return CFBridgingRelease(properties);
+}
+
+#pragma private
+
+- (void)_updateSource {
+    switch (_type) {
+        case YYImageTypeWebP: {
+            [self _updateSourceWebP];
+        } break;
+            
+        case YYImageTypePNG: {
+            [self _updateSourceAPNG];
+        } break;
+            
+        default: {
+            [self _updateSourceImageIO];
+        } break;
+    }
+}
+
+- (void)_updateSourceWebP {
+#if YYIMAGE_WEBP_ENABLED
+    _width = 0;
+    _height = 0;
+    _loopCount = 0;
+    if (_webpSource) WebPDemuxDelete(_webpSource);
+    _webpSource = NULL;
+    dispatch_semaphore_wait(_framesLock, DISPATCH_TIME_FOREVER);
+    _frames = nil;
+    dispatch_semaphore_signal(_framesLock);
+    
+    /*
+     https://developers.google.com/speed/webp/docs/api
+     The documentation said we can use WebPIDecoder to decode webp progressively, 
+     but currently it can only returns an empty image (not same as progressive jpegs),
+     so we don't use progressive decoding.
+     
+     When using WebPDecode() to decode multi-frame webp, we will get the error
+     "VP8_STATUS_UNSUPPORTED_FEATURE", so we first use WebPDemuxer to unpack it.
+     */
+    
+    WebPData webPData = {0};
+    webPData.bytes = _data.bytes;
+    webPData.size = _data.length;
+    WebPDemuxer *demuxer = WebPDemux(&webPData);
+    if (!demuxer) return;
+    
+    uint32_t webpFrameCount = WebPDemuxGetI(demuxer, WEBP_FF_FRAME_COUNT);
+    uint32_t webpLoopCount =  WebPDemuxGetI(demuxer, WEBP_FF_LOOP_COUNT);
+    uint32_t canvasWidth = WebPDemuxGetI(demuxer, WEBP_FF_CANVAS_WIDTH);
+    uint32_t canvasHeight = WebPDemuxGetI(demuxer, WEBP_FF_CANVAS_HEIGHT);
+    if (webpFrameCount == 0 || canvasWidth < 1 || canvasHeight < 1) {
+        WebPDemuxDelete(demuxer);
+        return;
+    }
+    
+    NSMutableArray *frames = [NSMutableArray new];
+    BOOL needBlend = NO;
+    uint32_t iterIndex = 0;
+    uint32_t lastBlendIndex = 0;
+    WebPIterator iter = {0};
+    if (WebPDemuxGetFrame(demuxer, 1, &iter)) { // one-based index...
+        do {
+            _YYImageDecoderFrame *frame = [_YYImageDecoderFrame new];
+            [frames addObject:frame];
+            if (iter.dispose_method == WEBP_MUX_DISPOSE_BACKGROUND) {
+                frame.dispose = YYImageDisposeBackground;
+            }
+            if (iter.blend_method == WEBP_MUX_BLEND) {
+                frame.blend = YYImageBlendOver;
+            }
+            
+            int canvasWidth = WebPDemuxGetI(demuxer, WEBP_FF_CANVAS_WIDTH);
+            int canvasHeight = WebPDemuxGetI(demuxer, WEBP_FF_CANVAS_HEIGHT);
+            frame.index = iterIndex;
+            frame.duration = iter.duration / 1000.0;
+            frame.width = iter.width;
+            frame.height = iter.height;
+            frame.hasAlpha = iter.has_alpha;
+            frame.blend = iter.blend_method == WEBP_MUX_BLEND;
+            frame.offsetX = iter.x_offset;
+            frame.offsetY = canvasHeight - iter.y_offset - iter.height;
+            
+            BOOL sizeEqualsToCanvas = (iter.width == canvasWidth && iter.height == canvasHeight);
+            BOOL offsetIsZero = (iter.x_offset == 0 && iter.y_offset == 0);
+            frame.isFullSize = (sizeEqualsToCanvas && offsetIsZero);
+            
+            if ((!frame.blend || !frame.hasAlpha) && frame.isFullSize) {
+                frame.blendFromIndex = lastBlendIndex = iterIndex;
+            } else {
+                if (frame.dispose && frame.isFullSize) {
+                    frame.blendFromIndex = lastBlendIndex;
+                    lastBlendIndex = iterIndex + 1;
+                } else {
+                    frame.blendFromIndex = lastBlendIndex;
+                }
+            }
+            if (frame.index != frame.blendFromIndex) needBlend = YES;
+            iterIndex++;
+        } while (WebPDemuxNextFrame(&iter));
+        WebPDemuxReleaseIterator(&iter);
+    }
+    if (frames.count != webpFrameCount) {
+        WebPDemuxDelete(demuxer);
+        return;
+    }
+    
+    _width = canvasWidth;
+    _height = canvasHeight;
+    _frameCount = frames.count;
+    _loopCount = webpLoopCount;
+    _needBlend = needBlend;
+    _webpSource = demuxer;
+    dispatch_semaphore_wait(_framesLock, DISPATCH_TIME_FOREVER);
+    _frames = frames;
+    dispatch_semaphore_signal(_framesLock);
+#else
+    static const char *func = __FUNCTION__;
+    static const int line = __LINE__;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        NSLog(@"[%s: %d] WebP is not available, check the documentation to see how to install WebP component: https://github.com/ibireme/YYImage#installation", func, line);
+    });
+#endif
+}
+
+- (void)_updateSourceAPNG {
+    /*
+     APNG extends PNG format to support animation, it was supported by ImageIO
+     since iOS 8.
+     
+     We use a custom APNG decoder to make APNG available in old system, so we
+     ignore the ImageIO's APNG frame info. Typically the custom decoder is a bit
+     faster than ImageIO.
+     */
+    
+    yy_png_info_release(_apngSource);
+    _apngSource = nil;
+    
+    [self _updateSourceImageIO]; // decode first frame
+    if (_frameCount == 0) return; // png decode failed
+    if (!_finalized) return; // ignore multi-frame before finalized
+    
+    yy_png_info *apng = yy_png_info_create(_data.bytes, (uint32_t)_data.length);
+    if (!apng) return; // apng decode failed
+    if (apng->apng_frame_num == 0 ||
+        (apng->apng_frame_num == 1 && apng->apng_first_frame_is_cover)) {
+        yy_png_info_release(apng);
+        return; // no animation
+    }
+    if (_source) { // apng decode succeed, no longer need image souce
+        CFRelease(_source);
+        _source = NULL;
+    }
+    
+    uint32_t canvasWidth = apng->header.width;
+    uint32_t canvasHeight = apng->header.height;
+    NSMutableArray *frames = [NSMutableArray new];
+    BOOL needBlend = NO;
+    uint32_t lastBlendIndex = 0;
+    for (uint32_t i = 0; i < apng->apng_frame_num; i++) {
+        _YYImageDecoderFrame *frame = [_YYImageDecoderFrame new];
+        [frames addObject:frame];
+        
+        yy_png_frame_info *fi = apng->apng_frames + i;
+        frame.index = i;
+        frame.duration = yy_png_delay_to_seconds(fi->frame_control.delay_num, fi->frame_control.delay_den);
+        frame.hasAlpha = YES;
+        frame.width = fi->frame_control.width;
+        frame.height = fi->frame_control.height;
+        frame.offsetX = fi->frame_control.x_offset;
+        frame.offsetY = canvasHeight - fi->frame_control.y_offset - fi->frame_control.height;
+        
+        BOOL sizeEqualsToCanvas = (frame.width == canvasWidth && frame.height == canvasHeight);
+        BOOL offsetIsZero = (fi->frame_control.x_offset == 0 && fi->frame_control.y_offset == 0);
+        frame.isFullSize = (sizeEqualsToCanvas && offsetIsZero);
+        
+        switch (fi->frame_control.dispose_op) {
+            case YY_PNG_DISPOSE_OP_BACKGROUND: {
+                frame.dispose = YYImageDisposeBackground;
+            } break;
+            case YY_PNG_DISPOSE_OP_PREVIOUS: {
+                frame.dispose = YYImageDisposePrevious;
+            } break;
+            default: {
+                frame.dispose = YYImageDisposeNone;
+            } break;
+        }
+        switch (fi->frame_control.blend_op) {
+            case YY_PNG_BLEND_OP_OVER: {
+                frame.blend = YYImageBlendOver;
+            } break;
+                
+            default: {
+                frame.blend = YYImageBlendNone;
+            } break;
+        }
+        
+        if (frame.blend == YYImageBlendNone && frame.isFullSize) {
+            frame.blendFromIndex  = i;
+            if (frame.dispose != YYImageDisposePrevious) lastBlendIndex = i;
+        } else {
+            if (frame.dispose == YYImageDisposeBackground && frame.isFullSize) {
+                frame.blendFromIndex = lastBlendIndex;
+                lastBlendIndex = i + 1;
+            } else {
+                frame.blendFromIndex = lastBlendIndex;
+            }
+        }
+        if (frame.index != frame.blendFromIndex) needBlend = YES;
+    }
+    
+    _width = canvasWidth;
+    _height = canvasHeight;
+    _frameCount = frames.count;
+    _loopCount = apng->apng_loop_num;
+    _needBlend = needBlend;
+    _apngSource = apng;
+    dispatch_semaphore_wait(_framesLock, DISPATCH_TIME_FOREVER);
+    _frames = frames;
+    dispatch_semaphore_signal(_framesLock);
+}
+
+- (void)_updateSourceImageIO {
+    _width = 0;
+    _height = 0;
+    _orientation = UIImageOrientationUp;
+    _loopCount = 0;
+    dispatch_semaphore_wait(_framesLock, DISPATCH_TIME_FOREVER);
+    _frames = nil;
+    dispatch_semaphore_signal(_framesLock);
+    
+    if (!_source) {
+        if (_finalized) {
+            _source = CGImageSourceCreateWithData((__bridge CFDataRef)_data, NULL);
+        } else {
+            _source = CGImageSourceCreateIncremental(NULL);
+            if (_source) CGImageSourceUpdateData(_source, (__bridge CFDataRef)_data, false);
+        }
+    } else {
+        CGImageSourceUpdateData(_source, (__bridge CFDataRef)_data, _finalized);
+    }
+    if (!_source) return;
+    
+    _frameCount = CGImageSourceGetCount(_source);
+    if (_frameCount == 0) return;
+    
+    if (!_finalized) { // ignore multi-frame before finalized
+        _frameCount = 1;
+    } else {
+        if (_type == YYImageTypePNG) { // use custom apng decoder and ignore multi-frame
+            _frameCount = 1;
+        }
+        if (_type == YYImageTypeGIF) { // get gif loop count
+            CFDictionaryRef properties = CGImageSourceCopyProperties(_source, NULL);
+            if (properties) {
+                CFDictionaryRef gif = CFDictionaryGetValue(properties, kCGImagePropertyGIFDictionary);
+                if (gif) {
+                    CFTypeRef loop = CFDictionaryGetValue(gif, kCGImagePropertyGIFLoopCount);
+                    if (loop) CFNumberGetValue(loop, kCFNumberNSIntegerType, &_loopCount);
+                }
+                CFRelease(properties);
+            }
+        }
+    }
+
+    /*
+     ICO, GIF, APNG may contains multi-frame.
+     */
+    NSMutableArray *frames = [NSMutableArray new];
+    for (NSUInteger i = 0; i < _frameCount; i++) {
+        _YYImageDecoderFrame *frame = [_YYImageDecoderFrame new];
+        frame.index = i;
+        frame.blendFromIndex = i;
+        frame.hasAlpha = YES;
+        frame.isFullSize = YES;
+        [frames addObject:frame];
+        
+        CFDictionaryRef properties = CGImageSourceCopyPropertiesAtIndex(_source, i, NULL);
+        if (properties) {
+            NSTimeInterval duration = 0;
+            NSInteger orientationValue = 0, width = 0, height = 0;
+            CFTypeRef value = NULL;
+            
+            value = CFDictionaryGetValue(properties, kCGImagePropertyPixelWidth);
+            if (value) CFNumberGetValue(value, kCFNumberNSIntegerType, &width);
+            value = CFDictionaryGetValue(properties, kCGImagePropertyPixelHeight);
+            if (value) CFNumberGetValue(value, kCFNumberNSIntegerType, &height);
+            if (_type == YYImageTypeGIF) {
+                CFDictionaryRef gif = CFDictionaryGetValue(properties, kCGImagePropertyGIFDictionary);
+                if (gif) {
+                    // Use the unclamped frame delay if it exists.
+                    value = CFDictionaryGetValue(gif, kCGImagePropertyGIFUnclampedDelayTime);
+                    if (!value) {
+                        // Fall back to the clamped frame delay if the unclamped frame delay does not exist.
+                        value = CFDictionaryGetValue(gif, kCGImagePropertyGIFDelayTime);
+                    }
+                    if (value) CFNumberGetValue(value, kCFNumberDoubleType, &duration);
+                }
+            }
+            
+            frame.width = width;
+            frame.height = height;
+            frame.duration = duration;
+            
+            if (i == 0 && _width + _height == 0) { // init first frame
+                _width = width;
+                _height = height;
+                value = CFDictionaryGetValue(properties, kCGImagePropertyOrientation);
+                if (value) {
+                    CFNumberGetValue(value, kCFNumberNSIntegerType, &orientationValue);
+                    _orientation = YYUIImageOrientationFromEXIFValue(orientationValue);
+                }
+            }
+            CFRelease(properties);
+        }
+    }
+    dispatch_semaphore_wait(_framesLock, DISPATCH_TIME_FOREVER);
+    _frames = frames;
+    dispatch_semaphore_signal(_framesLock);
+}
+
+- (CGImageRef)_newUnblendedImageAtIndex:(NSUInteger)index
+                         extendToCanvas:(BOOL)extendToCanvas
+                                decoded:(BOOL *)decoded CF_RETURNS_RETAINED {
+    
+    if (!_finalized && index > 0) return NULL;
+    if (_frames.count <= index) return NULL;
+    _YYImageDecoderFrame *frame = _frames[index];
+    
+    if (_source) {
+        CGImageRef imageRef = CGImageSourceCreateImageAtIndex(_source, index, (CFDictionaryRef)@{(id)kCGImageSourceShouldCache:@(YES)});
+        if (imageRef && extendToCanvas) {
+            size_t width = CGImageGetWidth(imageRef);
+            size_t height = CGImageGetHeight(imageRef);
+            if (width == _width && height == _height) {
+                CGImageRef imageRefExtended = YYCGImageCreateDecodedCopy(imageRef, YES);
+                if (imageRefExtended) {
+                    CFRelease(imageRef);
+                    imageRef = imageRefExtended;
+                    if (decoded) *decoded = YES;
+                }
+            } else {
+                CGContextRef context = CGBitmapContextCreate(NULL, _width, _height, 8, 0, YYCGColorSpaceGetDeviceRGB(), kCGBitmapByteOrder32Host | kCGImageAlphaPremultipliedFirst);
+                if (context) {
+                    CGContextDrawImage(context, CGRectMake(0, _height - height, width, height), imageRef);
+                    CGImageRef imageRefExtended = CGBitmapContextCreateImage(context);
+                    CFRelease(context);
+                    if (imageRefExtended) {
+                        CFRelease(imageRef);
+                        imageRef = imageRefExtended;
+                        if (decoded) *decoded = YES;
+                    }
+                }
+            }
+        }
+        return imageRef;
+    }
+    
+    if (_apngSource) {
+        uint32_t size = 0;
+        uint8_t *bytes = yy_png_copy_frame_data_at_index(_data.bytes, _apngSource, (uint32_t)index, &size);
+        if (!bytes) return NULL;
+        CGDataProviderRef provider = CGDataProviderCreateWithData(bytes, bytes, size, YYCGDataProviderReleaseDataCallback);
+        if (!provider) {
+            free(bytes);
+            return NULL;
+        }
+        bytes = NULL; // hold by provider
+        
+        CGImageSourceRef source = CGImageSourceCreateWithDataProvider(provider, NULL);
+        if (!source) {
+            CFRelease(provider);
+            return NULL;
+        }
+        CFRelease(provider);
+        
+        if(CGImageSourceGetCount(source) < 1) {
+            CFRelease(source);
+            return NULL;
+        }
+        
+        CGImageRef imageRef = CGImageSourceCreateImageAtIndex(source, 0, (CFDictionaryRef)@{(id)kCGImageSourceShouldCache:@(YES)});
+        CFRelease(source);
+        if (!imageRef) return NULL;
+        if (extendToCanvas) {
+            CGContextRef context = CGBitmapContextCreate(NULL, _width, _height, 8, 0, YYCGColorSpaceGetDeviceRGB(), kCGBitmapByteOrder32Host | kCGImageAlphaPremultipliedFirst); //bgrA
+            if (context) {
+                CGContextDrawImage(context, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height), imageRef);
+                CFRelease(imageRef);
+                imageRef = CGBitmapContextCreateImage(context);
+                CFRelease(context);
+                if (decoded) *decoded = YES;
+            }
+        }
+        return imageRef;
+    }
+    
+#if YYIMAGE_WEBP_ENABLED
+    if (_webpSource) {
+        WebPIterator iter;
+        if (!WebPDemuxGetFrame(_webpSource, (int)(index + 1), &iter)) return NULL; // demux webp frame data
+        // frame numbers are one-based in webp -----------^
+        
+        int frameWidth = iter.width;
+        int frameHeight = iter.height;
+        if (frameWidth < 1 || frameHeight < 1) return NULL;
+        
+        int width = extendToCanvas ? (int)_width : frameWidth;
+        int height = extendToCanvas ? (int)_height : frameHeight;
+        if (width > _width || height > _height) return NULL;
+        
+        const uint8_t *payload = iter.fragment.bytes;
+        size_t payloadSize = iter.fragment.size;
+        
+        WebPDecoderConfig config;
+        if (!WebPInitDecoderConfig(&config)) {
+            WebPDemuxReleaseIterator(&iter);
+            return NULL;
+        }
+        if (WebPGetFeatures(payload , payloadSize, &config.input) != VP8_STATUS_OK) {
+            WebPDemuxReleaseIterator(&iter);
+            return NULL;
+        }
+        
+        size_t bitsPerComponent = 8;
+        size_t bitsPerPixel = 32;
+        size_t bytesPerRow = YYImageByteAlign(bitsPerPixel / 8 * width, 32);
+        size_t length = bytesPerRow * height;
+        CGBitmapInfo bitmapInfo = kCGBitmapByteOrder32Host | kCGImageAlphaPremultipliedFirst; //bgrA
+        
+        void *pixels = calloc(1, length);
+        if (!pixels) {
+            WebPDemuxReleaseIterator(&iter);
+            return NULL;
+        }
+        
+        config.output.colorspace = MODE_bgrA;
+        config.output.is_external_memory = 1;
+        config.output.u.RGBA.rgba = pixels;
+        config.output.u.RGBA.stride = (int)bytesPerRow;
+        config.output.u.RGBA.size = length;
+        VP8StatusCode result = WebPDecode(payload, payloadSize, &config); // decode
+        if ((result != VP8_STATUS_OK) && (result != VP8_STATUS_NOT_ENOUGH_DATA)) {
+            WebPDemuxReleaseIterator(&iter);
+            free(pixels);
+            return NULL;
+        }
+        WebPDemuxReleaseIterator(&iter);
+        
+        if (extendToCanvas && (iter.x_offset != 0 || iter.y_offset != 0)) {
+            void *tmp = calloc(1, length);
+            if (tmp) {
+                vImage_Buffer src = {pixels, height, width, bytesPerRow};
+                vImage_Buffer dest = {tmp, height, width, bytesPerRow};
+                vImage_CGAffineTransform transform = {1, 0, 0, 1, iter.x_offset, -iter.y_offset};
+                uint8_t backColor[4] = {0};
+                vImage_Error error = vImageAffineWarpCG_ARGB8888(&src, &dest, NULL, &transform, backColor, kvImageBackgroundColorFill);
+                if (error == kvImageNoError) {
+                    memcpy(pixels, tmp, length);
+                }
+                free(tmp);
+            }
+        }
+        
+        CGDataProviderRef provider = CGDataProviderCreateWithData(pixels, pixels, length, YYCGDataProviderReleaseDataCallback);
+        if (!provider) {
+            free(pixels);
+            return NULL;
+        }
+        pixels = NULL; // hold by provider
+        
+        CGImageRef image = CGImageCreate(width, height, bitsPerComponent, bitsPerPixel, bytesPerRow, YYCGColorSpaceGetDeviceRGB(), bitmapInfo, provider, NULL, false, kCGRenderingIntentDefault);
+        CFRelease(provider);
+        if (decoded) *decoded = YES;
+        return image;
+    }
+#endif
+    
+    return NULL;
+}
+
+- (BOOL)_createBlendContextIfNeeded {
+    if (!_blendCanvas) {
+        _blendFrameIndex = NSNotFound;
+        _blendCanvas = CGBitmapContextCreate(NULL, _width, _height, 8, 0, YYCGColorSpaceGetDeviceRGB(), kCGBitmapByteOrder32Host | kCGImageAlphaPremultipliedFirst);
+    }
+    BOOL suc = _blendCanvas != NULL;
+    return suc;
+}
+
+- (void)_blendImageWithFrame:(_YYImageDecoderFrame *)frame {
+    if (frame.dispose == YYImageDisposePrevious) {
+        // nothing
+    } else if (frame.dispose == YYImageDisposeBackground) {
+        CGContextClearRect(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height));
+    } else { // no dispose
+        if (frame.blend == YYImageBlendOver) {
+            CGImageRef unblendImage = [self _newUnblendedImageAtIndex:frame.index extendToCanvas:NO decoded:NULL];
+            if (unblendImage) {
+                CGContextDrawImage(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height), unblendImage);
+                CFRelease(unblendImage);
+            }
+        } else {
+            CGContextClearRect(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height));
+            CGImageRef unblendImage = [self _newUnblendedImageAtIndex:frame.index extendToCanvas:NO decoded:NULL];
+            if (unblendImage) {
+                CGContextDrawImage(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height), unblendImage);
+                CFRelease(unblendImage);
+            }
+        }
+    }
+}
+
+- (CGImageRef)_newBlendedImageWithFrame:(_YYImageDecoderFrame *)frame CF_RETURNS_RETAINED{
+    CGImageRef imageRef = NULL;
+    if (frame.dispose == YYImageDisposePrevious) {
+        if (frame.blend == YYImageBlendOver) {
+            CGImageRef previousImage = CGBitmapContextCreateImage(_blendCanvas);
+            CGImageRef unblendImage = [self _newUnblendedImageAtIndex:frame.index extendToCanvas:NO decoded:NULL];
+            if (unblendImage) {
+                CGContextDrawImage(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height), unblendImage);
+                CFRelease(unblendImage);
+            }
+            imageRef = CGBitmapContextCreateImage(_blendCanvas);
+            CGContextClearRect(_blendCanvas, CGRectMake(0, 0, _width, _height));
+            if (previousImage) {
+                CGContextDrawImage(_blendCanvas, CGRectMake(0, 0, _width, _height), previousImage);
+                CFRelease(previousImage);
+            }
+        } else {
+            CGImageRef previousImage = CGBitmapContextCreateImage(_blendCanvas);
+            CGImageRef unblendImage = [self _newUnblendedImageAtIndex:frame.index extendToCanvas:NO decoded:NULL];
+            if (unblendImage) {
+                CGContextClearRect(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height));
+                CGContextDrawImage(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height), unblendImage);
+                CFRelease(unblendImage);
+            }
+            imageRef = CGBitmapContextCreateImage(_blendCanvas);
+            CGContextClearRect(_blendCanvas, CGRectMake(0, 0, _width, _height));
+            if (previousImage) {
+                CGContextDrawImage(_blendCanvas, CGRectMake(0, 0, _width, _height), previousImage);
+                CFRelease(previousImage);
+            }
+        }
+    } else if (frame.dispose == YYImageDisposeBackground) {
+        if (frame.blend == YYImageBlendOver) {
+            CGImageRef unblendImage = [self _newUnblendedImageAtIndex:frame.index extendToCanvas:NO decoded:NULL];
+            if (unblendImage) {
+                CGContextDrawImage(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height), unblendImage);
+                CFRelease(unblendImage);
+            }
+            imageRef = CGBitmapContextCreateImage(_blendCanvas);
+            CGContextClearRect(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height));
+        } else {
+            CGImageRef unblendImage = [self _newUnblendedImageAtIndex:frame.index extendToCanvas:NO decoded:NULL];
+            if (unblendImage) {
+                CGContextClearRect(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height));
+                CGContextDrawImage(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height), unblendImage);
+                CFRelease(unblendImage);
+            }
+            imageRef = CGBitmapContextCreateImage(_blendCanvas);
+            CGContextClearRect(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height));
+        }
+    } else { // no dispose
+        if (frame.blend == YYImageBlendOver) {
+            CGImageRef unblendImage = [self _newUnblendedImageAtIndex:frame.index extendToCanvas:NO decoded:NULL];
+            if (unblendImage) {
+                CGContextDrawImage(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height), unblendImage);
+                CFRelease(unblendImage);
+            }
+            imageRef = CGBitmapContextCreateImage(_blendCanvas);
+        } else {
+            CGImageRef unblendImage = [self _newUnblendedImageAtIndex:frame.index extendToCanvas:NO decoded:NULL];
+            if (unblendImage) {
+                CGContextClearRect(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height));
+                CGContextDrawImage(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height), unblendImage);
+                CFRelease(unblendImage);
+            }
+            imageRef = CGBitmapContextCreateImage(_blendCanvas);
+        }
+    }
+    return imageRef;
+}
+
+@end
+
+
+////////////////////////////////////////////////////////////////////////////////
+#pragma mark - Encoder
+
+@implementation YYImageEncoder {
+    NSMutableArray *_images;
+    NSMutableArray *_durations;
+}
+
+- (instancetype)init {
+    @throw [NSException exceptionWithName:@"YYImageEncoder init error" reason:@"YYImageEncoder must be initialized with a type. Use 'initWithType:' instead." userInfo:nil];
+    return [self initWithType:YYImageTypeUnknown];
+}
+
+- (instancetype)initWithType:(YYImageType)type {
+    if (type == YYImageTypeUnknown || type >= YYImageTypeOther) {
+        NSLog(@"[%s: %d] Unsupported image type:%d",__FUNCTION__, __LINE__, (int)type);
+        return nil;
+    }
+    
+#if !YYIMAGE_WEBP_ENABLED
+    if (type == YYImageTypeWebP) {
+        NSLog(@"[%s: %d] WebP is not available, check the documentation to see how to install WebP component: https://github.com/ibireme/YYImage#installation", __FUNCTION__, __LINE__);
+        return nil;
+    }
+#endif
+    
+    self = [super init];
+    if (!self) return nil;
+    _type = type;
+    _images = [NSMutableArray new];
+    _durations = [NSMutableArray new];
+
+    switch (type) {
+        case YYImageTypeJPEG:
+        case YYImageTypeJPEG2000: {
+            _quality = 0.9;
+        } break;
+        case YYImageTypeTIFF:
+        case YYImageTypeBMP:
+        case YYImageTypeGIF:
+        case YYImageTypeICO:
+        case YYImageTypeICNS:
+        case YYImageTypePNG: {
+            _quality = 1;
+            _lossless = YES;
+        } break;
+        case YYImageTypeWebP: {
+            _quality = 0.8;
+        } break;
+        default:
+            break;
+    }
+    
+    return self;
+}
+
+- (void)setQuality:(CGFloat)quality {
+    _quality = quality < 0 ? 0 : quality > 1 ? 1 : quality;
+}
+
+- (void)addImage:(UIImage *)image duration:(NSTimeInterval)duration {
+    if (!image.CGImage) return;
+    duration = duration < 0 ? 0 : duration;
+    [_images addObject:image];
+    [_durations addObject:@(duration)];
+}
+
+- (void)addImageWithData:(NSData *)data duration:(NSTimeInterval)duration {
+    if (data.length == 0) return;
+    duration = duration < 0 ? 0 : duration;
+    [_images addObject:data];
+    [_durations addObject:@(duration)];
+}
+
+- (void)addImageWithFile:(NSString *)path duration:(NSTimeInterval)duration {
+    if (path.length == 0) return;
+    duration = duration < 0 ? 0 : duration;
+    NSURL *url = [NSURL URLWithString:path];
+    if (!url) return;
+    [_images addObject:url];
+    [_durations addObject:@(duration)];
+}
+
+- (BOOL)_imageIOAvaliable {
+    switch (_type) {
+        case YYImageTypeJPEG:
+        case YYImageTypeJPEG2000:
+        case YYImageTypeTIFF:
+        case YYImageTypeBMP:
+        case YYImageTypeICO:
+        case YYImageTypeICNS:
+        case YYImageTypeGIF: {
+            return _images.count > 0;
+        } break;
+        case YYImageTypePNG: {
+            return _images.count == 1;
+        } break;
+        case YYImageTypeWebP: {
+            return NO;
+        } break;
+        default: return NO;
+    }
+}
+
+- (CGImageDestinationRef)_newImageDestination:(id)dest imageCount:(NSUInteger)count CF_RETURNS_RETAINED {
+    if (!dest) return nil;
+    CGImageDestinationRef destination = NULL;
+    if ([dest isKindOfClass:[NSString class]]) {
+        NSURL *url = [[NSURL alloc] initFileURLWithPath:dest];
+        if (url) {
+            destination = CGImageDestinationCreateWithURL((CFURLRef)url, YYImageTypeToUTType(_type), count, NULL);
+        }
+    } else if ([dest isKindOfClass:[NSMutableData class]]) {
+        destination = CGImageDestinationCreateWithData((CFMutableDataRef)dest, YYImageTypeToUTType(_type), count, NULL);
+    }
+    return destination;
+}
+
+- (void)_encodeImageWithDestination:(CGImageDestinationRef)destination imageCount:(NSUInteger)count {
+    if (_type == YYImageTypeGIF) {
+        NSDictionary *gifProperty = @{(__bridge id)kCGImagePropertyGIFDictionary:
+                                        @{(__bridge id)kCGImagePropertyGIFLoopCount: @(_loopCount)}};
+        CGImageDestinationSetProperties(destination, (__bridge CFDictionaryRef)gifProperty);
+    }
+    
+    for (int i = 0; i < count; i++) {
+        @autoreleasepool {
+            id imageSrc = _images[i];
+            NSDictionary *frameProperty = NULL;
+            if (_type == YYImageTypeGIF && count > 1) {
+                frameProperty = @{(NSString *)kCGImagePropertyGIFDictionary : @{(NSString *) kCGImagePropertyGIFDelayTime:_durations[i]}};
+            } else {
+                frameProperty = @{(id)kCGImageDestinationLossyCompressionQuality : @(_quality)};
+            }
+            
+            if ([imageSrc isKindOfClass:[UIImage class]]) {
+                UIImage *image = imageSrc;
+                if (image.imageOrientation != UIImageOrientationUp && image.CGImage) {
+                    CGBitmapInfo info = CGImageGetBitmapInfo(image.CGImage) | CGImageGetAlphaInfo(image.CGImage);
+                    CGImageRef rotated = YYCGImageCreateCopyWithOrientation(image.CGImage, image.imageOrientation, info);
+                    if (rotated) {
+                        image = [UIImage imageWithCGImage:rotated];
+                        CFRelease(rotated);
+                    }
+                }
+                if (image.CGImage) CGImageDestinationAddImage(destination, ((UIImage *)imageSrc).CGImage, (CFDictionaryRef)frameProperty);
+            } else if ([imageSrc isKindOfClass:[NSURL class]]) {
+                CGImageSourceRef source = CGImageSourceCreateWithURL((CFURLRef)imageSrc, NULL);
+                if (source) {
+                    CGImageDestinationAddImageFromSource(destination, source, 0, (CFDictionaryRef)frameProperty);
+                    CFRelease(source);
+                }
+            } else if ([imageSrc isKindOfClass:[NSData class]]) {
+                CGImageSourceRef source = CGImageSourceCreateWithData((CFDataRef)imageSrc, NULL);
+                if (source) {
+                    CGImageDestinationAddImageFromSource(destination, source, 0, (CFDictionaryRef)frameProperty);
+                    CFRelease(source);
+                }
+            }
+        }
+    }
+}
+
+- (CGImageRef)_newCGImageFromIndex:(NSUInteger)index decoded:(BOOL)decoded CF_RETURNS_RETAINED {
+    UIImage *image = nil;
+    id imageSrc= _images[index];
+    if ([imageSrc isKindOfClass:[UIImage class]]) {
+        image = imageSrc;
+    } else if ([imageSrc isKindOfClass:[NSURL class]]) {
+        image = [UIImage imageWithContentsOfFile:((NSURL *)imageSrc).absoluteString];
+    } else if ([imageSrc isKindOfClass:[NSData class]]) {
+        image = [UIImage imageWithData:imageSrc];
+    }
+    if (!image) return NULL;
+    CGImageRef imageRef = image.CGImage;
+    if (!imageRef) return NULL;
+    if (image.imageOrientation != UIImageOrientationUp) {
+        return YYCGImageCreateCopyWithOrientation(imageRef, image.imageOrientation, kCGBitmapByteOrder32Host | kCGImageAlphaPremultipliedFirst);
+    }
+    if (decoded) {
+        return YYCGImageCreateDecodedCopy(imageRef, YES);
+    }
+    return (CGImageRef)CFRetain(imageRef);
+}
+
+- (NSData *)_encodeWithImageIO {
+    NSMutableData *data = [NSMutableData new];
+    NSUInteger count = _type == YYImageTypeGIF ? _images.count : 1;
+    CGImageDestinationRef destination = [self _newImageDestination:data imageCount:count];
+    BOOL suc = NO;
+    if (destination) {
+        [self _encodeImageWithDestination:destination imageCount:count];
+        suc = CGImageDestinationFinalize(destination);
+        CFRelease(destination);
+    }
+    if (suc && data.length > 0) {
+        return data;
+    } else {
+        return nil;
+    }
+}
+
+- (BOOL)_encodeWithImageIO:(NSString *)path {
+    NSUInteger count = _type == YYImageTypeGIF ? _images.count : 1;
+    CGImageDestinationRef destination = [self _newImageDestination:path imageCount:count];
+    BOOL suc = NO;
+    if (destination) {
+        [self _encodeImageWithDestination:destination imageCount:count];
+        suc = CGImageDestinationFinalize(destination);
+        CFRelease(destination);
+    }
+    return suc;
+}
+
+- (NSData *)_encodeAPNG {
+    // encode APNG (ImageIO doesn't support APNG encoding, so we use a custom encoder)
+    NSMutableArray *pngDatas = [NSMutableArray new];
+    NSMutableArray *pngSizes = [NSMutableArray new];
+    NSUInteger canvasWidth = 0, canvasHeight = 0;
+    for (int i = 0; i < _images.count; i++) {
+        CGImageRef decoded = [self _newCGImageFromIndex:i decoded:YES];
+        if (!decoded) return nil;
+        CGSize size = CGSizeMake(CGImageGetWidth(decoded), CGImageGetHeight(decoded));
+        [pngSizes addObject:[NSValue valueWithCGSize:size]];
+        if (canvasWidth < size.width) canvasWidth = size.width;
+        if (canvasHeight < size.height) canvasHeight = size.height;
+        CFDataRef frameData = YYCGImageCreateEncodedData(decoded, YYImageTypePNG, 1);
+        CFRelease(decoded);
+        if (!frameData) return nil;
+        [pngDatas addObject:(__bridge id)(frameData)];
+        CFRelease(frameData);
+        if (size.width < 1 || size.height < 1) return nil;
+    }
+    CGSize firstFrameSize = [(NSValue *)[pngSizes firstObject] CGSizeValue];
+    if (firstFrameSize.width < canvasWidth || firstFrameSize.height < canvasHeight) {
+        CGImageRef decoded = [self _newCGImageFromIndex:0 decoded:YES];
+        if (!decoded) return nil;
+        CGContextRef context = CGBitmapContextCreate(NULL, canvasWidth, canvasHeight, 8,
+                                                     0, YYCGColorSpaceGetDeviceRGB(), kCGBitmapByteOrder32Host | kCGImageAlphaPremultipliedFirst);
+        if (!context) {
+            CFRelease(decoded);
+            return nil;
+        }
+        CGContextDrawImage(context, CGRectMake(0, canvasHeight - firstFrameSize.height, firstFrameSize.width, firstFrameSize.height), decoded);
+        CFRelease(decoded);
+        CGImageRef extendedImage = CGBitmapContextCreateImage(context);
+        CFRelease(context);
+        if (!extendedImage) return nil;
+        CFDataRef frameData = YYCGImageCreateEncodedData(extendedImage, YYImageTypePNG, 1);
+        if (!frameData) {
+            CFRelease(extendedImage);
+            return nil;
+        }
+        pngDatas[0] = (__bridge id)(frameData);
+        CFRelease(frameData);
+    }
+    
+    NSData *firstFrameData = pngDatas[0];
+    yy_png_info *info = yy_png_info_create(firstFrameData.bytes, (uint32_t)firstFrameData.length);
+    if (!info) return nil;
+    NSMutableData *result = [NSMutableData new];
+    BOOL insertBefore = NO, insertAfter = NO;
+    uint32_t apngSequenceIndex = 0;
+    
+    uint32_t png_header[2];
+    png_header[0] = YY_FOUR_CC(0x89, 0x50, 0x4E, 0x47);
+    png_header[1] = YY_FOUR_CC(0x0D, 0x0A, 0x1A, 0x0A);
+    
+    [result appendBytes:png_header length:8];
+    
+    for (int i = 0; i < info->chunk_num; i++) {
+        yy_png_chunk_info *chunk = info->chunks + i;
+        
+        if (!insertBefore && chunk->fourcc == YY_FOUR_CC('I', 'D', 'A', 'T')) {
+            insertBefore = YES;
+            // insert acTL (APNG Control)
+            uint32_t acTL[5] = {0};
+            acTL[0] = yy_swap_endian_uint32(8); //length
+            acTL[1] = YY_FOUR_CC('a', 'c', 'T', 'L'); // fourcc
+            acTL[2] = yy_swap_endian_uint32((uint32_t)pngDatas.count); // num frames
+            acTL[3] = yy_swap_endian_uint32((uint32_t)_loopCount); // num plays
+            acTL[4] = yy_swap_endian_uint32((uint32_t)crc32(0, (const Bytef *)(acTL + 1), 12)); //crc32
+            [result appendBytes:acTL length:20];
+            
+            // insert fcTL (first frame control)
+            yy_png_chunk_fcTL chunk_fcTL = {0};
+            chunk_fcTL.sequence_number = apngSequenceIndex;
+            chunk_fcTL.width = (uint32_t)firstFrameSize.width;
+            chunk_fcTL.height = (uint32_t)firstFrameSize.height;
+            yy_png_delay_to_fraction([(NSNumber *)_durations[0] doubleValue], &chunk_fcTL.delay_num, &chunk_fcTL.delay_den);
+            chunk_fcTL.delay_num = chunk_fcTL.delay_num;
+            chunk_fcTL.delay_den = chunk_fcTL.delay_den;
+            chunk_fcTL.dispose_op = YY_PNG_DISPOSE_OP_BACKGROUND;
+            chunk_fcTL.blend_op = YY_PNG_BLEND_OP_SOURCE;
+            
+            uint8_t fcTL[38] = {0};
+            *((uint32_t *)fcTL) = yy_swap_endian_uint32(26); //length
+            *((uint32_t *)(fcTL + 4)) = YY_FOUR_CC('f', 'c', 'T', 'L'); // fourcc
+            yy_png_chunk_fcTL_write(&chunk_fcTL, fcTL + 8);
+            *((uint32_t *)(fcTL + 34)) = yy_swap_endian_uint32((uint32_t)crc32(0, (const Bytef *)(fcTL + 4), 30));
+            [result appendBytes:fcTL length:38];
+            
+            apngSequenceIndex++;
+        }
+        
+        if (!insertAfter && insertBefore && chunk->fourcc != YY_FOUR_CC('I', 'D', 'A', 'T')) {
+            insertAfter = YES;
+            // insert fcTL and fdAT (APNG frame control and data)
+            
+            for (int i = 1; i < pngDatas.count; i++) {
+                NSData *frameData = pngDatas[i];
+                yy_png_info *frame = yy_png_info_create(frameData.bytes, (uint32_t)frameData.length);
+                if (!frame) {
+                    yy_png_info_release(info);
+                    return nil;
+                }
+                
+                // insert fcTL (first frame control)
+                yy_png_chunk_fcTL chunk_fcTL = {0};
+                chunk_fcTL.sequence_number = apngSequenceIndex;
+                chunk_fcTL.width = frame->header.width;
+                chunk_fcTL.height = frame->header.height;
+                yy_png_delay_to_fraction([(NSNumber *)_durations[i] doubleValue], &chunk_fcTL.delay_num, &chunk_fcTL.delay_den);
+                chunk_fcTL.delay_num = chunk_fcTL.delay_num;
+                chunk_fcTL.delay_den = chunk_fcTL.delay_den;
+                chunk_fcTL.dispose_op = YY_PNG_DISPOSE_OP_BACKGROUND;
+                chunk_fcTL.blend_op = YY_PNG_BLEND_OP_SOURCE;
+                
+                uint8_t fcTL[38] = {0};
+                *((uint32_t *)fcTL) = yy_swap_endian_uint32(26); //length
+                *((uint32_t *)(fcTL + 4)) = YY_FOUR_CC('f', 'c', 'T', 'L'); // fourcc
+                yy_png_chunk_fcTL_write(&chunk_fcTL, fcTL + 8);
+                *((uint32_t *)(fcTL + 34)) = yy_swap_endian_uint32((uint32_t)crc32(0, (const Bytef *)(fcTL + 4), 30));
+                [result appendBytes:fcTL length:38];
+                
+                apngSequenceIndex++;
+                
+                // insert fdAT (frame data)
+                for (int d = 0; d < frame->chunk_num; d++) {
+                    yy_png_chunk_info *dchunk = frame->chunks + d;
+                    if (dchunk->fourcc == YY_FOUR_CC('I', 'D', 'A', 'T')) {
+                        uint32_t length = yy_swap_endian_uint32(dchunk->length + 4);
+                        [result appendBytes:&length length:4]; //length
+                        uint32_t fourcc = YY_FOUR_CC('f', 'd', 'A', 'T');
+                        [result appendBytes:&fourcc length:4]; //fourcc
+                        uint32_t sq = yy_swap_endian_uint32(apngSequenceIndex);
+                        [result appendBytes:&sq length:4]; //data (sq)
+                        [result appendBytes:(((uint8_t *)frameData.bytes) + dchunk->offset + 8) length:dchunk->length]; //data
+                        uint8_t *bytes = ((uint8_t *)result.bytes) + result.length - dchunk->length - 8;
+                        uint32_t crc = yy_swap_endian_uint32((uint32_t)crc32(0, bytes, dchunk->length + 8));
+                        [result appendBytes:&crc length:4]; //crc
+                        
+                        apngSequenceIndex++;
+                    }
+                }
+                yy_png_info_release(frame);
+            }
+        }
+        
+        [result appendBytes:((uint8_t *)firstFrameData.bytes) + chunk->offset length:chunk->length + 12];
+    }
+    yy_png_info_release(info);
+    return result;
+}
+
+- (NSData *)_encodeWebP {
+#if YYIMAGE_WEBP_ENABLED
+    // encode webp
+    NSMutableArray *webpDatas = [NSMutableArray new];
+    for (NSUInteger i = 0; i < _images.count; i++) {
+        CGImageRef image = [self _newCGImageFromIndex:i decoded:NO];
+        if (!image) return nil;
+        CFDataRef frameData = YYCGImageCreateEncodedWebPData(image, _lossless, _quality, 4, YYImagePresetDefault);
+        CFRelease(image);
+        if (!frameData) return nil;
+        [webpDatas addObject:(__bridge id)frameData];
+        CFRelease(frameData);
+    }
+    if (webpDatas.count == 1) {
+        return webpDatas.firstObject;
+    } else {
+        // multi-frame webp
+        WebPMux *mux = WebPMuxNew();
+        if (!mux) return nil;
+        for (NSUInteger i = 0; i < _images.count; i++) {
+            NSData *data = webpDatas[i];
+            NSNumber *duration = _durations[i];
+            WebPMuxFrameInfo frame = {0};
+            frame.bitstream.bytes = data.bytes;
+            frame.bitstream.size = data.length;
+            frame.duration = (int)(duration.floatValue * 1000.0);
+            frame.id = WEBP_CHUNK_ANMF;
+            frame.dispose_method = WEBP_MUX_DISPOSE_BACKGROUND;
+            frame.blend_method = WEBP_MUX_NO_BLEND;
+            if (WebPMuxPushFrame(mux, &frame, 0) != WEBP_MUX_OK) {
+                WebPMuxDelete(mux);
+                return nil;
+            }
+        }
+        
+        WebPMuxAnimParams params = {(uint32_t)0, (int)_loopCount};
+        if (WebPMuxSetAnimationParams(mux, &params) != WEBP_MUX_OK) {
+            WebPMuxDelete(mux);
+            return nil;
+        }
+        
+        WebPData output_data;
+        WebPMuxError error = WebPMuxAssemble(mux, &output_data);
+        WebPMuxDelete(mux);
+        if (error != WEBP_MUX_OK) {
+            return nil;
+        }
+        NSData *result = [NSData dataWithBytes:output_data.bytes length:output_data.size];
+        WebPDataClear(&output_data);
+        return result.length ? result : nil;
+    }
+#else
+    return nil;
+#endif
+}
+- (NSData *)encode {
+    if (_images.count == 0) return nil;
+    
+    if ([self _imageIOAvaliable]) return [self _encodeWithImageIO];
+    if (_type == YYImageTypePNG) return [self _encodeAPNG];
+    if (_type == YYImageTypeWebP) return [self _encodeWebP];
+    return nil;
+}
+
+- (BOOL)encodeToFile:(NSString *)path {
+    if (_images.count == 0 || path.length == 0) return NO;
+    
+    if ([self _imageIOAvaliable]) return [self _encodeWithImageIO:path];
+    NSData *data = [self encode];
+    if (!data) return NO;
+    return [data writeToFile:path atomically:YES];
+}
+
++ (NSData *)encodeImage:(UIImage *)image type:(YYImageType)type quality:(CGFloat)quality {
+    YYImageEncoder *encoder = [[YYImageEncoder alloc] initWithType:type];
+    encoder.quality = quality;
+    [encoder addImage:image duration:0];
+    return [encoder encode];
+}
+
++ (NSData *)encodeImageWithDecoder:(YYImageDecoder *)decoder type:(YYImageType)type quality:(CGFloat)quality {
+    if (!decoder || decoder.frameCount == 0) return nil;
+    YYImageEncoder *encoder = [[YYImageEncoder alloc] initWithType:type];
+    encoder.quality = quality;
+    for (int i = 0; i < decoder.frameCount; i++) {
+        UIImage *frame = [decoder frameAtIndex:i decodeForDisplay:YES].image;
+        [encoder addImageWithData:UIImagePNGRepresentation(frame) duration:[decoder frameDurationAtIndex:i]];
+    }
+    return encoder.encode;
+}
+
+@end
+
+
+@implementation UIImage (YYImageCoder)
+
+- (instancetype)yy_imageByDecoded {
+    if (self.yy_isDecodedForDisplay) return self;
+    CGImageRef imageRef = self.CGImage;
+    if (!imageRef) return self;
+    CGImageRef newImageRef = YYCGImageCreateDecodedCopy(imageRef, YES);
+    if (!newImageRef) return self;
+    UIImage *newImage = [[self.class alloc] initWithCGImage:newImageRef scale:self.scale orientation:self.imageOrientation];
+    CGImageRelease(newImageRef);
+    if (!newImage) newImage = self; // decode failed, return self.
+    newImage.yy_isDecodedForDisplay = YES;
+    return newImage;
+}
+
+- (BOOL)yy_isDecodedForDisplay {
+    if (self.images.count > 1 || [self isKindOfClass:[YYSpriteSheetImage class]]) return YES;
+    NSNumber *num = objc_getAssociatedObject(self, @selector(yy_isDecodedForDisplay));
+    return [num boolValue];
+}
+
+- (void)setYy_isDecodedForDisplay:(BOOL)isDecodedForDisplay {
+    objc_setAssociatedObject(self, @selector(yy_isDecodedForDisplay), @(isDecodedForDisplay), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+}
+
+- (void)yy_saveToAlbumWithCompletionBlock:(void(^)(NSURL *assetURL, NSError *error))completionBlock {
+    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+        NSData *data = [self _yy_dataRepresentationForSystem:YES];
+        ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
+        [library writeImageDataToSavedPhotosAlbum:data metadata:nil completionBlock:^(NSURL *assetURL, NSError *error){
+            if (!completionBlock) return;
+            if (pthread_main_np()) {
+                completionBlock(assetURL, error);
+            } else {
+                dispatch_async(dispatch_get_main_queue(), ^{
+                    completionBlock(assetURL, error);
+                });
+            }
+        }];
+    });
+}
+
+- (NSData *)yy_imageDataRepresentation {
+    return [self _yy_dataRepresentationForSystem:NO];
+}
+
+/// @param forSystem YES: used for system album (PNG/JPEG/GIF), NO: used for YYImage (PNG/JPEG/GIF/WebP)
+- (NSData *)_yy_dataRepresentationForSystem:(BOOL)forSystem {
+    NSData *data = nil;
+    if ([self isKindOfClass:[YYImage class]]) {
+        YYImage *image = (id)self;
+        if (image.animatedImageData) {
+            if (forSystem) { // system only support GIF and PNG
+                if (image.animatedImageType == YYImageTypeGIF ||
+                    image.animatedImageType == YYImageTypePNG) {
+                    data = image.animatedImageData;
+                }
+            } else {
+                data = image.animatedImageData;
+            }
+        }
+    }
+    if (!data) {
+        CGImageRef imageRef = self.CGImage ? (CGImageRef)CFRetain(self.CGImage) : nil;
+        if (imageRef) {
+            CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
+            CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo(imageRef) & kCGBitmapAlphaInfoMask;
+            BOOL hasAlpha = NO;
+            if (alphaInfo == kCGImageAlphaPremultipliedLast ||
+                alphaInfo == kCGImageAlphaPremultipliedFirst ||
+                alphaInfo == kCGImageAlphaLast ||
+                alphaInfo == kCGImageAlphaFirst) {
+                hasAlpha = YES;
+            }
+            if (self.imageOrientation != UIImageOrientationUp) {
+                CGImageRef rotated = YYCGImageCreateCopyWithOrientation(imageRef, self.imageOrientation, bitmapInfo | alphaInfo);
+                if (rotated) {
+                    CFRelease(imageRef);
+                    imageRef = rotated;
+                }
+            }
+            @autoreleasepool {
+                UIImage *newImage = [UIImage imageWithCGImage:imageRef];
+                if (newImage) {
+                    if (hasAlpha) {
+                        data = UIImagePNGRepresentation([UIImage imageWithCGImage:imageRef]);
+                    } else {
+                        data = UIImageJPEGRepresentation([UIImage imageWithCGImage:imageRef], 0.9); // same as Apple's example
+                    }
+                }
+            }
+            CFRelease(imageRef);
+        }
+    }
+    if (!data) {
+        data = UIImagePNGRepresentation(self);
+    }
+    return data;
+}
+
+@end

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