Merge pull request #1070 from AFNetworking/experimental-background-image-inflation

Improved Image Loading Performance By Inflating Image In Background

AFNetworking/AFImageRequestOperation.h

@@ -65,6 +65,11 @@
  The scale factor used when interpreting the image data to construct `responseImage`. Specifying a scale factor of 1.0 results in an image whose size matches the pixel-based dimensions of the image. Applying a different scale factor changes the size of the image as reported by the size property. This is set to the value of scale of the main screen by default, which automatically scales images for retina displays, for instance.
  */
 @property (nonatomic, assign) CGFloat imageScale;
+
+/**
+ Whether to automatically inflate response image data for compressed formats (such as PNG or JPEG). Enabling this can significantly improve drawing performance on iOS when used with `setCompletionBlockWithSuccess:failure:`, as it allows a bitmap representation to be constructed in the background rather than on the main thread. `YES` by default.
+ */
+@property (nonatomic, assign) BOOL automaticallyInflatesResponseImage;
 #endif
 
 /**

AFNetworking/AFImageRequestOperation.m

@@ -32,6 +32,90 @@ static dispatch_queue_t image_request_operation_processing_queue() {
     return af_image_request_operation_processing_queue;
 }
 
+#if defined(__IPHONE_OS_VERSION_MIN_REQUIRED)
+#import <CoreGraphics/CoreGraphics.h>
+
+static UIImage * AFImageWithDataAtScale(NSData *data, CGFloat scale) {
+    if ([UIImage instancesRespondToSelector:@selector(initWithData:scale:)]) {
+        return [[UIImage alloc] initWithData:data scale:scale];
+    } else {
+        UIImage *image = [[UIImage alloc] initWithData:data];
+        return [[UIImage alloc] initWithCGImage:[image CGImage] scale:scale orientation:image.imageOrientation];
+    }
+}
+
+static UIImage * AFInflatedImageFromResponseWithDataAtScale(NSHTTPURLResponse *response, NSData *data, CGFloat scale) {
+    if (!data || [data length] == 0) {
+        return nil;
+    }
+
+    CGImageRef imageRef;
+
+    CGDataProviderRef dataProvider = CGDataProviderCreateWithCFData((__bridge CFDataRef)data);
+
+    NSSet *contentTypes = AFContentTypesFromHTTPHeader([[response allHeaderFields] valueForKey:@"Content-Type"]);
+    if ([contentTypes containsObject:@"image/png"]) {
+        imageRef = CGImageCreateWithPNGDataProvider(dataProvider,  NULL, true, kCGRenderingIntentDefault);
+    } else if ([contentTypes containsObject:@"image/jpeg"]) {
+        imageRef = CGImageCreateWithJPEGDataProvider(dataProvider, NULL, true, kCGRenderingIntentDefault);
+    } else {
+        UIImage *image = AFImageWithDataAtScale(data, scale);
+        if (image.images) {
+            CGDataProviderRelease(dataProvider);
+            
+            return image;
+        }
+        
+        imageRef = CGImageCreateCopy([image CGImage]);
+    }
+
+    CGDataProviderRelease(dataProvider);
+
+    if (!imageRef) {
+        return nil;
+    }
+
+    size_t width = CGImageGetWidth(imageRef);
+    size_t height = CGImageGetHeight(imageRef);
+    size_t bitsPerComponent = CGImageGetBitsPerComponent(imageRef);
+    size_t bytesPerRow = NULL; // CGImageGetBytesPerRow() calculates incorrectly in iOS 5.0, so defer to CGBitmapContextCreate()
+    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
+    CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
+
+    if (CGColorSpaceGetNumberOfComponents(colorSpace) == 3) {
+        int alpha = (bitmapInfo & kCGBitmapAlphaInfoMask);
+        if (alpha == kCGImageAlphaNone) {
+            bitmapInfo &= ~kCGBitmapAlphaInfoMask;
+            bitmapInfo |= kCGImageAlphaNoneSkipFirst;
+        } else if (!(alpha == kCGImageAlphaNoneSkipFirst || alpha == kCGImageAlphaNoneSkipLast)) {
+            bitmapInfo &= ~kCGBitmapAlphaInfoMask;
+            bitmapInfo |= kCGImageAlphaPremultipliedFirst;
+        }
+    }
+
+    CGContextRef context = CGBitmapContextCreate(NULL, width, height, bitsPerComponent, bytesPerRow, colorSpace, bitmapInfo);
+
+    CGColorSpaceRelease(colorSpace);
+
+    if (!context) {
+        CGImageRelease(imageRef);
+
+        return [[UIImage alloc] initWithData:data];
+    }
+
+    CGRect rect = CGRectMake(0.0f, 0.0f, width, height);
+    CGContextDrawImage(context, rect, imageRef);
+    CGImageRef inflatedImageRef = CGBitmapContextCreateImage(context);
+    CGContextRelease(context);
+
+    UIImage *inflatedImage = [[UIImage alloc] initWithCGImage:inflatedImageRef scale:scale orientation:UIImageOrientationUp];
+    CGImageRelease(inflatedImageRef);
+    CGImageRelease(imageRef);
+    
+    return inflatedImage;
+}
+#endif
+
 @interface AFImageRequestOperation ()
 #if defined(__IPHONE_OS_VERSION_MIN_REQUIRED)
 @property (readwrite, nonatomic, strong) UIImage *responseImage;
@@ -142,6 +226,7 @@ static dispatch_queue_t image_request_operation_processing_queue() {
 
 #if defined(__IPHONE_OS_VERSION_MIN_REQUIRED)
     self.imageScale = [[UIScreen mainScreen] scale];
+    self.automaticallyInflatesResponseImage = YES;
 #endif
 
     return self;
@@ -151,9 +236,11 @@ static dispatch_queue_t image_request_operation_processing_queue() {
 #if defined(__IPHONE_OS_VERSION_MIN_REQUIRED)
 - (UIImage *)responseImage {
     if (!_responseImage && [self.responseData length] > 0 && [self isFinished]) {
-        UIImage *image = [UIImage imageWithData:self.responseData];
-
-        self.responseImage = [UIImage imageWithCGImage:[image CGImage] scale:self.imageScale orientation:image.imageOrientation];
+        if (self.automaticallyInflatesResponseImage) {
+            self.responseImage = AFInflatedImageFromResponseWithDataAtScale(self.response, self.responseData, self.imageScale);
+        } else {
+            self.responseImage = AFImageWithDataAtScale(self.responseData, self.imageScale);
+        }
     }
 
     return _responseImage;