Add pluggable image processing system

Examples/UIExplorer/UIExplorerUnitTests/RCTImageLoaderHelpers.h

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+/**
+ * The examples provided by Facebook are for non-commercial testing and
+ * evaluation purposes only.
+ *
+ * Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON INFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#import "RCTImageLoader.h"
+
+typedef BOOL (^RCTImageURLLoaderCanLoadImageURLHandler)(NSURL *requestURL);
+typedef RCTImageLoaderCancellationBlock (^RCTImageURLLoaderLoadImageURLHandler)(NSURL *imageURL, CGSize size, CGFloat scale, UIViewContentMode resizeMode, RCTImageLoaderProgressBlock progressHandler, RCTImageLoaderCompletionBlock completionHandler);
+
+@interface RCTConcreteImageURLLoader : NSObject <RCTImageURLLoader>
+
+- (instancetype)initWithPriority:(float)priority
+          canLoadImageURLHandler:(RCTImageURLLoaderCanLoadImageURLHandler)canLoadImageURLHandler
+             loadImageURLHandler:(RCTImageURLLoaderLoadImageURLHandler)loadImageURLHandler;
+
+@end
+
+typedef BOOL (^RCTImageDecoderCanDecodeImageDataHandler)(NSData *imageData);
+typedef RCTImageLoaderCancellationBlock (^RCTImageDecoderDecodeImageDataHandler)(NSData *imageData, CGSize size, CGFloat scale, UIViewContentMode resizeMode, RCTImageLoaderCompletionBlock completionHandler);
+
+@interface RCTConcreteImageDecoder : NSObject <RCTImageDecoder>
+
+- (instancetype)initWithPriority:(float)priority
+       canDecodeImageDataHandler:(RCTImageDecoderCanDecodeImageDataHandler)canDecodeImageDataHandler
+          decodeImageDataHandler:(RCTImageDecoderDecodeImageDataHandler)decodeImageDataHandler;
+
+@end
+
+#define _RCTDefineImageHandler(SUPERCLASS, CLASS_NAME) \
+@interface CLASS_NAME : SUPERCLASS @end \
+@implementation CLASS_NAME RCT_EXPORT_MODULE() @end
+
+#define RCTDefineImageURLLoader(CLASS_NAME) \
+_RCTDefineImageHandler(RCTConcreteImageURLLoader, CLASS_NAME)
+
+#define RCTDefineImageDecoder(CLASS_NAME) \
+_RCTDefineImageHandler(RCTConcreteImageDecoder, CLASS_NAME)