替换iOS ALAssetsLibrary中的ALAsset对象 [英] Replace ALAsset object in iOS ALAssetsLibrary

问题描述

我正在开发一个应用程序，它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。我成功读取数据，通过使用writeImageDataToSavedPhotosAlbum函数操作和写入库。问题是，不是更新原始图像，它创建一个新的。

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]; //这是NSData可能是你想要的
 
 if（！EXIFDictionary）{
 //如果图像没有EXIF字典（不是所有的图像），然后创建一个我们使用
 EXIFDictionary = [NSMutableDictionary dictionary]; 
} 
 if（！GPSDictionary）{
 GPSDictionary = [NSMutableDictionary dictionary]; 
} 
 if（！TIFFDictionray）{
 TIFFDictionray = [NSMutableDictionary dictionary]; 
} 
 
 
 [TIFFDictionray setObject：@这应该是图像描述forKey：（NSString *）kCGImagePropertyTIFFImageDescription]; 
 [EXIFDictionary setObject：@这应该是用户注释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 ：日期]）; 
 [date release]; 
}]; 
 
 [...] 
  

提前感谢

解决方案

您只能更改应用程式已建立的相片（请参阅可编辑属性 ALAsset ）。为此，请在代表照片的 ALAsset 上调用 setImageData：metadata：completionBlock： b
$ b

还有一个 writeModifiedImageDataToSavedPhotosAlbum：metadata：completionBlock：方法，但它总是创建一个新的资产，资产（我不确定如何使用这些信息）。

I am developing an application that reads the geo location of an image and allows the user to modify this information and write this data back. I successfully read the data, manipulate and write to the library by using writeImageDataToSavedPhotosAlbum function. The problem is that instead updating the original image, it creates a new one.

How could i replace or update that item ?

[...]

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];
}];

[...]

Thanks in advance

解决方案

You can only change photos that your app has created (see the documentation on the editable property of ALAsset). To do so, call setImageData:metadata:completionBlock: on the ALAsset that represents the photo.

There's also a writeModifiedImageDataToSavedPhotosAlbum:metadata:completionBlock: method, but it always creates a new asset that is considered a modified version of the original asset (I'm not exactly sure how that information is used).

这篇关于替换iOS ALAssetsLibrary中的ALAsset对象的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！