Using the WebPDemux API to support progressive animated WebP. This is less performance but at least works

Author: dreampiggy

Example/SDWebImageWebPCoderExample/ViewController.m

@@ -22,6 +22,8 @@ - (void)viewDidLoad {
     [super viewDidLoad];
     // Do any additional setup after loading the view, typically from a nib.
 
+    [SDImageCache.sharedImageCache clearDiskOnCompletion:nil];
+    
     [[SDImageCodersManager sharedManager] addCoder:[SDImageWebPCoder sharedCoder]];
 
     self.imageView1 = [UIImageView new];
@@ -46,7 +48,7 @@ - (void)viewDidLoad {
             }
         });
     }];
-    [self.imageView2 sd_setImageWithURL:animatedWebPURL completed:^(UIImage * _Nullable image, NSError * _Nullable error, SDImageCacheType cacheType, NSURL * _Nullable imageURL) {
+    [self.imageView2 sd_setImageWithURL:animatedWebPURL placeholderImage:nil options:SDWebImageProgressiveLoad completed:^(UIImage * _Nullable image, NSError * _Nullable error, SDImageCacheType cacheType, NSURL * _Nullable imageURL) {
         if (image) {
             NSLog(@"%@", @"Animated WebP load success");
         }

SDWebImageWebPCoder/Classes/SDImageWebPCoder.m

@@ -86,6 +86,7 @@ @implementation SDWebPCoderFrame
 @implementation SDImageWebPCoder {
     WebPIDecoder *_idec;
     WebPDemuxer *_demux;
+    WebPData *_webpdata; // Copied for progressive animation demuxer
     NSData *_imageData;
     CGFloat _scale;
     NSUInteger _loopCount;
@@ -113,6 +114,10 @@ - (void)dealloc {
         WebPDemuxDelete(_demux);
         _demux = NULL;
     }
+    if (_webpdata) {
+        WebPDataClear(_webpdata);
+        _webpdata = NULL;
+    }
     if (_canvas) {
         CGContextRelease(_canvas);
         _canvas = NULL;
@@ -290,6 +295,8 @@ - (instancetype)initIncrementalWithOptions:(nullable SDImageCoderOptions *)optio
             preserveAspectRatio = preserveAspectRatioValue.boolValue;
         }
         _preserveAspectRatio = preserveAspectRatio;
+        _currentBlendIndex = NSNotFound;
+        _lock = dispatch_semaphore_create(1);
     }
     return self;
 }
@@ -300,11 +307,41 @@ - (void)updateIncrementalData:(NSData *)data finished:(BOOL)finished {
     }
     _imageData = data;
     _finished = finished;
-    VP8StatusCode status = WebPIUpdate(_idec, data.bytes, data.length);
-    if (status != VP8_STATUS_OK && status != VP8_STATUS_SUSPENDED) {
-        return;
+    if (!_demux) {
+        VP8StatusCode status = WebPIUpdate(_idec, data.bytes, data.length);
+        if (status == VP8_STATUS_OK || status == VP8_STATUS_SUSPENDED) {
+            return;
+        }
+        // This case may be Animated WebP progressive decode
+        if (status == VP8_STATUS_UNSUPPORTED_FEATURE) {
+            WebPDemuxState state;
+            WebPData tmpData;
+            WebPDataInit(&tmpData);
+            tmpData.bytes = data.bytes;
+            tmpData.size = data.length;
+            // Copy to avoid the NSData dealloc and VP8 internal retain the pointer
+            _webpdata = malloc(sizeof(WebPData));
+            WebPDataCopy(&tmpData, _webpdata);
+            _demux = WebPDemuxPartial(_webpdata, &state);
+        }
+    } else {
+        // libwebp current have no API to update demuxer, so we always delete and recreate demuxer
+        WebPDemuxDelete(_demux);
+        _demux = NULL;
+        WebPDemuxState state;
+        WebPData tmpData;
+        WebPDataInit(&tmpData);
+        tmpData.bytes = data.bytes;
+        tmpData.size = data.length;
+        // Copy to avoid the NSData dealloc and VP8 internal retain the pointer
+        WebPDataClear(_webpdata);
+        WebPDataCopy(&tmpData, _webpdata);
+        _demux = WebPDemuxPartial(_webpdata, &state);
+    }
+    
+    if (_demux) {
+        [self scanAndCheckFramesValidWithDemuxer:_demux];
     }
-    // libwebp current does not support progressive decoding for animated image, so no need to scan and update the frame information
 }
 
 - (UIImage *)incrementalDecodedImageWithOptions:(SDImageCoderOptions *)options {
@@ -832,6 +869,10 @@ - (BOOL)scanAndCheckFramesValidWithDemuxer:(WebPDemuxer *)demuxer {
 
     // We should loop all the frames and scan each frames' blendFromIndex for later decoding, this can also ensure all frames is valid
     do {
+        if (!iter.complete) {
+            // Skip partial frame
+            continue;
+        }
         SDWebPCoderFrame *frame = [[SDWebPCoderFrame alloc] init];
         frame.index = iterIndex;
         frame.duration = [self sd_frameDurationWithIterator:iter];