用ALAsset获取相册原图

最近在用ALAsset获取相册时候，ALAsset的ALAssetRepresentation只提供了全尺寸图、全屏幕图、metadata等，但是将这些转换成NSData的时候，尺寸都不精确，不是变大了就是变小了。后来一想，不如直接由ALAsset转换成NSData，再由NSData转换成UIImage，后来一试试，真的可以了，而且图片的尺寸还是原来的尺寸。下面把代码贴上

/**
 *  ALAsset 直接转换为UIImage
 *
 *  @param asset
 *
 *  @return UIImage
 */
- (UIImage *)assetToImageForALAsset:(ALAsset *)asset{
    
    UIImage *tempImg = nil;
    ALAssetRepresentation *image_representation = [asset defaultRepresentation];
    Byte *buffer = (Byte*)malloc(image_representation.size);
    NSUInteger length = [image_representation getBytes:buffer fromOffset: 0.0 length:image_representation.size error:nil];
    if (length != 0)  {
        NSData *adata = [[NSData alloc] initWithBytesNoCopy:buffer length:image_representation.size freeWhenDone:YES];
        tempImg = [UIImage imageWithData:adata];
    }
    return tempImg;
}

 

//保存成jpg，图片会小一些

    BOOL result = [UIImageJPEGRepresentation(image, 1.0) writeToFile:filePath atomically:YES];