Decode WebP images directly into a buffer Core Animation likes

Source/Classes/Categories/PINImage+DecodedImage.m

@@ -122,12 +122,6 @@ + (PINImage *)pin_decodedImageWithData:(NSData *)data skipDecodeIfPossible:(BOOL
         return nil;
     }
 
-#if PIN_WEBP
-    if ([data pin_isWebP]) {
-        return [PINImage pin_imageWithWebPData:data];
-    }
-#endif
-
     PINImage *decodedImage = nil;
 
     CGImageSourceRef imageSourceRef = CGImageSourceCreateWithData((CFDataRef)data, NULL);
@@ -156,6 +150,12 @@ + (PINImage *)pin_decodedImageWithData:(NSData *)data skipDecodeIfPossible:(BOOL
         CFRelease(imageSourceRef);
     }
 
+#if PIN_WEBP
+    if (!decodedImage && [data pin_isWebP]) {
+        return [PINImage pin_imageWithWebPData:data];
+    }
+#endif
+
     return decodedImage;
 }
 

Source/Classes/Categories/PINImage+WebP.m

@@ -12,70 +12,95 @@
 
 #import "webp/decode.h"
 
-static void releaseData(void *info, const void *data, size_t size)
-{
-    WebPFree((void *)data);
+@implementation PINImage (PINWebP)
+
+static enum WEBP_CSP_MODE webp_cs_mode_from_cg_bitmap_info(CGBitmapInfo info, BOOL *fail) {
+    CGImageByteOrderInfo byteOrder = info & kCGBitmapByteOrderMask;
+    BOOL keepByteOrder;
+    switch (byteOrder) {
+        case kCGImageByteOrder32Big:
+            keepByteOrder = YES;
+            break;
+        case kCGImageByteOrder32Little:
+            keepByteOrder = NO;
+            break;
+        case kCGImageByteOrder16Big:
+        case kCGImageByteOrder16Little:
+        case kCGImageByteOrderDefault:
+        case kCGImageByteOrderMask:
+            *fail = YES;
+            return MODE_RGBA;
+    }
+
+    CGImageAlphaInfo ai = info & kCGBitmapAlphaInfoMask;
+    switch (ai) {
+        case kCGImageAlphaLast:
+        case kCGImageAlphaNoneSkipLast:
+            return keepByteOrder ? MODE_RGBA : MODE_ARGB;
+        case kCGImageAlphaNone:
+            return keepByteOrder ? MODE_RGB  : MODE_BGR;
+        case kCGImageAlphaFirst:
+        case kCGImageAlphaNoneSkipFirst:
+            return keepByteOrder ? MODE_ARGB : MODE_BGRA;
+        case kCGImageAlphaPremultipliedLast:
+            return keepByteOrder ? MODE_rgbA : MODE_Argb;
+        case kCGImageAlphaPremultipliedFirst:
+            return keepByteOrder ? MODE_Argb : MODE_rgbA;
+        case kCGImageAlphaOnly:
+            *fail = YES;
+            return MODE_RGB;
+    }
 }
 
-@implementation PINImage (PINWebP)
+#if PIN_TARGET_IOS
+#define PIN_WEBP_DECODE_CLEANUP() UIGraphicsEndImageContext()
+#elif PIN_TARGET_MAC
+#define PIN_WEBP_DECODE_CLEANUP() [image unlockFocus]
+#endif
 
+// We let the system decide all the bitmap options for us, so Core Animation won't have
+// to copy our images over to the render server. Use "Color Copied Images" in the iOS simulator to
+// detect this case.
 + (PINImage *)pin_imageWithWebPData:(NSData *)webPData
 {
-    WebPBitstreamFeatures features;
-    if (WebPGetFeatures([webPData bytes], [webPData length], &features) == VP8_STATUS_OK) {
-        // Decode the WebP image data into a RGBA value array
-        int height, width;
-        uint8_t *data = NULL;
-        int pixelLength = 0;
-
-        if (features.has_alpha) {
-            data = WebPDecodeRGBA([webPData bytes], [webPData length], &width, &height);
-            pixelLength = 4;
-        } else {
-            data = WebPDecodeRGB([webPData bytes], [webPData length], &width, &height);
-            pixelLength = 3;
-        }
-
-        if (data) {
-            CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, data, width * height * pixelLength, releaseData);
-
-            CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
-            CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
-
-            if (features.has_alpha) {
-                bitmapInfo |= kCGImageAlphaLast;
-            } else {
-                bitmapInfo |= kCGImageAlphaNone;
-            }
-
-            CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
-            CGImageRef imageRef = CGImageCreate(width,
-                                                height,
-                                                8,
-                                                8 * pixelLength,
-                                                pixelLength * width,
-                                                colorSpaceRef,
-                                                bitmapInfo,
-                                                provider,
-                                                NULL,
-                                                NO,
-                                                renderingIntent);
-
-            PINImage *image = nil;
+    WebPDecoderConfig cfg;
+    WebPInitDecoderConfig(&cfg);
+    if (WebPGetFeatures(webPData.bytes, webPData.length, &cfg.input) != VP8_STATUS_OK) {
+        return nil;
+    }
+    CGSize size = CGSizeMake(cfg.input.width, cfg.input.height);
+    CGContextRef ctx = NULL;
+    PINImage *image;
 #if PIN_TARGET_IOS
-            image = [UIImage imageWithCGImage:imageRef];
+    UIGraphicsBeginImageContextWithOptions(size, !cfg.input.has_alpha, 1.0);
+    ctx = UIGraphicsGetCurrentContext();
 #elif PIN_TARGET_MAC
-            image = [[self alloc] initWithCGImage:imageRef size:CGSizeZero];
+    image = [[NSImage alloc] initWithSize:NSSizeFromCGSize(size)];
+    [image lockFocus];
+    ctx = NSGraphicsContext.currentContext.CGContext;
 #endif
-            
-            CGImageRelease(imageRef);
-            CGColorSpaceRelease(colorSpaceRef);
-            CGDataProviderRelease(provider);
-            
-            return image;
-        }
+    NSAssert(ctx != NULL, @"Failed to get CG context.");
+    BOOL getColorspaceFailed = NO;
+    cfg.output.colorspace = webp_cs_mode_from_cg_bitmap_info(CGBitmapContextGetBitmapInfo(ctx),
+                                                             &getColorspaceFailed);
+    if (getColorspaceFailed) {
+        PIN_WEBP_DECODE_CLEANUP();
+        return nil;
     }
-    return nil;
+    cfg.output.width = cfg.input.width;
+    cfg.output.height = cfg.input.height;
+    cfg.output.is_external_memory = 1;
+    cfg.output.u.RGBA.rgba = (uint8_t *)CGBitmapContextGetData(ctx);
+    cfg.output.u.RGBA.stride = (int)CGBitmapContextGetBytesPerRow(ctx);
+    cfg.output.u.RGBA.size = cfg.output.u.RGBA.stride * cfg.input.height;
+    int status = WebPDecode(webPData.bytes, webPData.length, &cfg);
+#if PIN_TARGET_IOS
+    if (status == VP8_STATUS_OK) {
+        image = UIGraphicsGetImageFromCurrentImageContext();
+    }
+#endif
+    PIN_WEBP_DECODE_CLEANUP();
+    return status == VP8_STATUS_OK ? image : nil;
 }
 
 @end