替换 iOS ALAssetsLibrary 中的 ALAsset 对象

我正在开发一个应用程序，该应用程序读取图像的地理位置并允许用户修改此信息并将此数据写回。我使用 writeImageDataToSavedPhotosAlbum 函数成功读取数据、操作并写入库。问题在于，它不是更新原始图像，而是创建一个新图像。

我如何更换或更新该项目？

[...]

NSMutableDictionary *EXIFDictionary = [[[metadata objectForKey:(NSString *)kCGImagePropertyExifDictionary]mutableCopy]autorelease];
NSMutableDictionary *GPSDictionary  = [[[metadata objectForKey:(NSString *)kCGImagePropertyGPSDictionary]mutableCopy]autorelease];
NSMutableDictionary *TIFFDictionray = [[[metadata objectForKey:(NSString *)kCGImagePropertyTIFFDictionary]mutableCopy]autorelease];

Byte *buffer = (Byte*)malloc(representation.size);
NSUInteger buffered = [representation getBytes:buffer fromOffset:0.0 length:representation.size error:nil];
NSData *imageData = [NSData dataWithBytesNoCopy:buffer length:buffered freeWhenDone:YES]; //this is NSData may be what you want

if(!EXIFDictionary) {
    //if the image does not have an EXIF dictionary (not all images do), then create one for us to use
    EXIFDictionary = [NSMutableDictionary dictionary];
}
if(!GPSDictionary) {
    GPSDictionary = [NSMutableDictionary dictionary];
}
if(!TIFFDictionray) {
    TIFFDictionray = [NSMutableDictionary dictionary];
}


[TIFFDictionray setObject:@"This should be the image description" forKey:(NSString*)kCGImagePropertyTIFFImageDescription];
[EXIFDictionary setObject:@"This should be the user comment" forKey:(NSString*)kCGImagePropertyExifUserComment];

[metadataAsMutable setObject:TIFFDictionray forKey:(NSString*)kCGImagePropertyTIFFDictionary];
[metadataAsMutable setObject:EXIFDictionary forKey:(NSString*)kCGImagePropertyExifDictionary];

__block NSDate *date = [[NSDate date] retain];

ALAssetsLibrary *library = [[ALAssetsLibrary alloc]init];

[library writeImageDataToSavedPhotosAlbum:imageData metadata:metadataAsMutable completionBlock:^(NSURL *assetURL, NSError *error) {
    NSLog(@"Saving Time: %g", [[NSDate date] timeIntervalSinceDate:date]);
    [date release];
}];

[...]

提前致谢

您只能更改您的应用程序创建的照片（请参阅有关editable的财产ALAsset）。为此，请致电setImageData:metadata:completionBlock: on the ALAsset代表照片。

还有一个writeModifiedImageDataToSavedPhotosAlbum:metadata:completionBlock:方法，但它总是创建一个新资产，该资产被视为原始资产的修改版本（我不太确定如何使用该信息）。