react-native/Libraries/CameraRoll/RCTAssetsLibraryImageLoader.m

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2015-09-02 15:25:10 +00:00
/**
* Copyright (c) 2015-present, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*/
#import "RCTAssetsLibraryImageLoader.h"
#import <AssetsLibrary/AssetsLibrary.h>
#import <ImageIO/ImageIO.h>
#import <UIKit/UIKit.h>
#import "RCTBridge.h"
#import "RCTConvert.h"
#import "RCTImageLoader.h"
#import "RCTImageUtils.h"
#import "RCTUtils.h"
static dispatch_queue_t RCTAssetsLibraryImageLoaderQueue(void);
static UIImage *RCTScaledImageForAsset(ALAssetRepresentation *representation, CGSize size, CGFloat scale, UIViewContentMode resizeMode, NSError **error);
@implementation RCTAssetsLibraryImageLoader
{
ALAssetsLibrary *_assetsLibrary;
}
RCT_EXPORT_MODULE()
@synthesize bridge = _bridge;
- (ALAssetsLibrary *)assetsLibrary
{
return _assetsLibrary ?: (_assetsLibrary = [ALAssetsLibrary new]);
}
#pragma mark - RCTImageLoader
- (BOOL)canLoadImageURL:(NSURL *)requestURL
{
return [requestURL.scheme.lowercaseString isEqualToString:@"assets-library"];
}
- (RCTImageLoaderCancellationBlock)loadImageForURL:(NSURL *)imageURL size:(CGSize)size scale:(CGFloat)scale resizeMode:(UIViewContentMode)resizeMode progressHandler:(RCTImageLoaderProgressBlock)progressHandler completionHandler:(RCTImageLoaderCompletionBlock)completionHandler
{
[[self assetsLibrary] assetForURL:imageURL resultBlock:^(ALAsset *asset) {
if (asset) {
// ALAssetLibrary API is async and will be multi-threaded. Loading a few full
// resolution images at once will spike the memory up to store the image data,
// and might trigger memory warnings and/or OOM crashes.
// To improve this, process the loaded asset in a serial queue.
dispatch_async(RCTAssetsLibraryImageLoaderQueue(), ^{
// Also make sure the image is released immediately after it's used so it
// doesn't spike the memory up during the process.
@autoreleasepool {
BOOL useMaximumSize = CGSizeEqualToSize(size, CGSizeZero);
ALAssetRepresentation *representation = [asset defaultRepresentation];
UIImage *image;
NSError *error = nil;
if (useMaximumSize) {
image = [UIImage imageWithCGImage:representation.fullResolutionImage
scale:scale
orientation:(UIImageOrientation)representation.orientation];
} else {
image = RCTScaledImageForAsset(representation, size, scale, resizeMode, &error);
}
completionHandler(error, image);
}
});
} else {
NSString *errorText = [NSString stringWithFormat:@"Failed to load asset at URL %@ with no error message.", imageURL];
NSError *error = RCTErrorWithMessage(errorText);
completionHandler(error, nil);
}
} failureBlock:^(NSError *loadError) {
NSString *errorText = [NSString stringWithFormat:@"Failed to load asset at URL %@.\niOS Error: %@", imageURL, loadError];
NSError *error = RCTErrorWithMessage(errorText);
completionHandler(error, nil);
}];
return ^{};
}
@end
@implementation RCTBridge (RCTAssetsLibraryImageLoader)
- (RCTAssetsLibraryImageLoader *)assetsLibraryImageLoader
{
return self.modules[RCTBridgeModuleNameForClass([RCTAssetsLibraryImageLoader class])];
}
- (ALAssetsLibrary *)assetsLibrary
{
return [self.assetsLibraryImageLoader assetsLibrary];
}
@end
static dispatch_queue_t RCTAssetsLibraryImageLoaderQueue(void)
{
static dispatch_queue_t queue;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
queue = dispatch_queue_create("com.facebook.RCTAssetsLibraryImageLoader", DISPATCH_QUEUE_SERIAL);
});
return queue;
}
// Why use a custom scaling method? Greater efficiency, reduced memory overhead:
// http://www.mindsea.com/2012/12/downscaling-huge-alassets-without-fear-of-sigkill
static UIImage *RCTScaledImageForAsset(ALAssetRepresentation *representation, CGSize size, CGFloat scale, UIViewContentMode resizeMode, NSError **error)
{
NSUInteger length = (NSUInteger)representation.size;
NSMutableData *data = [NSMutableData dataWithLength:length];
if (![representation getBytes:data.mutableBytes
fromOffset:0
length:length
error:error]) {
return nil;
}
CGSize sourceSize = representation.dimensions;
CGSize targetSize = RCTTargetSize(sourceSize, representation.scale,
size, scale, resizeMode, NO);
NSDictionary *options = @{
(id)kCGImageSourceShouldAllowFloat: @YES,
(id)kCGImageSourceCreateThumbnailWithTransform: @YES,
(id)kCGImageSourceCreateThumbnailFromImageAlways: @YES,
(id)kCGImageSourceThumbnailMaxPixelSize: @(MAX(targetSize.width, targetSize.height) * scale)
};
CGImageSourceRef sourceRef = CGImageSourceCreateWithData((__bridge CFDataRef)data, nil);
CGImageRef imageRef = CGImageSourceCreateThumbnailAtIndex(sourceRef, 0, (__bridge CFDictionaryRef)options);
if (sourceRef) {
CFRelease(sourceRef);
}
if (imageRef) {
UIImage *image = [UIImage imageWithCGImage:imageRef scale:scale
orientation:UIImageOrientationUp];
CGImageRelease(imageRef);
return image;
}
return nil;
}