ios - 替换 iOS ALAssetsLibrary 中的 ALAsset 对象

Question

我正在开发一个应用程序来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、操作和写入库。问题是它不是更新原始图像，而是创建一个新图像。

我如何替换或更新该项目？

[...]

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

Answer 1

您只能更改您的应用创建的照片(请参阅有关 ALAsset 的 editable 属性的文档)。为此，请在表示照片的 ALAsset 上调用 setImageData:metadata:completionBlock:。

还有一个 writeModifiedImageDataToSavedPhotosAlbum:metadata:completionBlock: 方法，但它总是创建一个新 Assets ，该 Assets 被认为是原始 Assets 的修改版本(我不确定如何使用该信息).