storeImage时，需要获取context中的SDWebImageContextImageCoder

SDWebImage/Core/SDImageCache.m

@@ -279,7 +279,11 @@ static NSString * _defaultDiskCacheDirectory;
                     format = [SDImageCoderHelper CGImageContainsAlpha:image.CGImage] ? SDImageFormatPNG : SDImageFormatJPEG;
                 }
             }
-            NSData *encodedData = [[SDImageCodersManager sharedManager] encodedDataWithImage:image format:format options:context[SDWebImageContextImageEncodeOptions]];
+            id<SDImageCoder> imageCoder = context[SDWebImageContextImageCoder];
+            if (!imageCoder) {
+                imageCoder = [SDImageCodersManager sharedManager];
+            }
+            NSData *encodedData = [imageCoder encodedDataWithImage:image format:format options:context[SDWebImageContextImageEncodeOptions]];
             dispatch_async(self.ioQueue, ^{
                 [self _storeImageDataToDisk:encodedData forKey:key];
                 [self _archivedDataWithImage:image forKey:key];