我不是 fullScreenImage 或 fullResolutionImage 的粉丝。我发现当您对队列中的多个资产执行此操作时,即使您立即释放 UIImage,内存使用量也会急剧增加,而它不应该。此外,当使用 fullScreenImage 或 fullResolutionImage 时,返回的 UIImage 仍然是压缩的,这意味着它会在第一次绘制之前被解压缩,因此在主线程上会阻塞你的 UI。
我更喜欢使用这种方法。
-(UIImage *)fullSizeImageForAssetRepresentation:(ALAssetRepresentation *)assetRepresentation
{
UIImage *result = nil;
NSData *data = nil;
uint8_t *buffer = (uint8_t *)malloc(sizeof(uint8_t)*[assetRepresentation size]);
if (buffer != NULL) {
NSError *error = nil;
NSUInteger bytesRead = [assetRepresentation getBytes:buffer fromOffset:0 length:[assetRepresentation size] error:&error];
data = [NSData dataWithBytes:buffer length:bytesRead];
free(buffer);
}
if ([data length])
{
CGImageSourceRef sourceRef = CGImageSourceCreateWithData((__bridge CFDataRef)data, nil);
NSMutableDictionary *options = [NSMutableDictionary dictionary];
[options setObject:(id)kCFBooleanTrue forKey:(id)kCGImageSourceShouldAllowFloat];
[options setObject:(id)kCFBooleanTrue forKey:(id)kCGImageSourceCreateThumbnailFromImageAlways];
[options setObject:(id)[NSNumber numberWithFloat:640.0f] forKey:(id)kCGImageSourceThumbnailMaxPixelSize];
//[options setObject:(id)kCFBooleanTrue forKey:(id)kCGImageSourceCreateThumbnailWithTransform];
CGImageRef imageRef = CGImageSourceCreateThumbnailAtIndex(sourceRef, 0, (__bridge CFDictionaryRef)options);
if (imageRef) {
result = [UIImage imageWithCGImage:imageRef scale:[assetRepresentation scale] orientation:(UIImageOrientation)[assetRepresentation orientation]];
CGImageRelease(imageRef);
}
if (sourceRef)
CFRelease(sourceRef);
}
return result;
}
你可以像这样使用它:
// Get the full image in a background thread
dispatch_async(dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
UIImage* image = [self fullSizeImageForAssetRepresentation:asset.defaultRepresentation];
dispatch_async(dispatch_get_main_queue(), ^{
// Do something with the UIImage
});
});