Merge pull request SDWebImage#936 from flexih/master

Decoding webp, depends on source image data alpha status.

Author: bpoplauschi

SDWebImage/UIImage+WebP.m

@@ -24,7 +24,11 @@ + (UIImage *)sd_imageWithWebPData:(NSData *)data {
         return nil;
     }
 
-    config.output.colorspace = MODE_rgbA;
+    if (WebPGetFeatures(data.bytes, data.length, &config.input) != VP8_STATUS_OK) {
+        return nil;
+    }
+
+    config.output.colorspace = config.input.has_alpha ? MODE_rgbA : MODE_RGB;
     config.options.use_threads = 1;
 
     // Decode the WebP image data into a RGBA value array.
@@ -43,9 +47,10 @@ + (UIImage *)sd_imageWithWebPData:(NSData *)data {
     CGDataProviderRef provider =
     CGDataProviderCreateWithData(NULL, config.output.u.RGBA.rgba, config.output.u.RGBA.size, FreeImageData);
     CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
-    CGBitmapInfo bitmapInfo = kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast;
+    CGBitmapInfo bitmapInfo = config.input.has_alpha ? kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast : 0;
+    size_t components = config.input.has_alpha ? 4 : 3;
     CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
-    CGImageRef imageRef = CGImageCreate(width, height, 8, 32, 4 * width, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);
+    CGImageRef imageRef = CGImageCreate(width, height, 8, components * 8, components * width, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);
 
     CGColorSpaceRelease(colorSpaceRef);
     CGDataProviderRelease(provider);