如何将图像从资产库移动到特定于应用程序的私有位置？

Question

这是我试过的代码片段:

[library    writeImageToSavedPhotosAlbum:self.checkInImage.CGImage metadata:self.metadata
            completionBlock             :^(NSURL * assetURL, NSError * error) {
        NSLog (@"Asset url = %@", assetURL);
         NSError *err;
        NSString *docDir = [NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
        NSString *jpgFilePath = [NSString stringWithFormat:@"%@/test.jpg", docDir];
        NSFileManager *fileManager = [NSFileManager defaultManager];
                [fileManager moveItemAtURL:assetURL toURL:[NSURL URLWithString:jpgFilePath] error:&err];
                NSLog(@"error is %@", err);
    }];

我收到错误,因为错误域= NSCocoaErrorDomain Code = 262"操作无法完成.(Cocoa错误262.)"UserInfo = 0xb49a680 {NSURL = assets-library://asset/asset.JPG？id = 6FAC823A- 33CB-489B-A125-714FBA5F0EE8&EXT = JPG}

有任何想法吗？

Answer 1

文档(和谷歌).此错误代码对应于NSFileReadUnsupportedSchemeError常量 - 即您不能仅使用assets-library://URL来使用NSFileManager移动文件.(关于ipod-library://URL 的情况也是如此.)您必须使用AssetsLibrary框架来获取文件的数据,然后使用它将其写入文件- [NSData writeToFile:atomically:].

ALAssetsLibrary *lib = [ALAssetsLibrary new];
[lib assetForUrl:theURL // the asset URL you have obtained, NSURL object
    resultBlock:^(ALAsset *asset) {
        // get data
        ALAssetRepresentation *repr = [asset defaultRepresentation];
        CGImageRef cgImg = [repr fullResolutionImage];
        NSString *fname = [repr fileName];
        UIImage *img = [UIImage imageWithCGImage:cgImg];
        NSData *data = UIImagePNGRepresentation(img);
        [data writeToFile:[@"BaseDirectory/" stringByAppendingPathComponent:fname]
            atomically:YES];
        [lib release];
    }
    failureBlock:^(NSError *error) {
        // recover from error, then
        [lib release];
    }];

Answer 2

这就是我解决问题的方法：

1）我将没有元数据的文件保存在某个位置，并存储其urlpath。

2）然后使用以下代码来保存带有元数据的同一文件。这里的 fileURL 是从步骤 1 中获取的 urlpath。

CFURLRef url = CFURLCreateFilePathURL(NULL, (CFURLRef)fileURL, NULL);
// Creating Image source from image url
CGImageSourceRef imageSource = CGImageSourceCreateWithURL(url, NULL);

// This will be the data CGImageDestinationRef will write into
CFMutableDataRef data = CFDataCreateMutable(kCFAllocatorDefault, 0);
CGImageDestinationRef imageDestination = CGImageDestinationCreateWithData(data, CFSTR("public.jpeg"), 1, NULL);

BOOL success = (imageSource != NULL);

require(success, cleanup);

success = (imageDestination != NULL);
require(success, cleanup);

// Add the image contained in the image source to the destination, overidding the old metadata with our modified metadata
NSDictionary *metadata = someObj.metadata;
CGImageDestinationAddImageFromSource(imageDestination, imageSource, 0, (CFDictionaryRef)metadata);

// Tell the destination to write the image data and metadata into our data object.
success = CGImageDestinationFinalize(imageDestination);

require(success, cleanup);

// Write the data into the url
[(NSMutableData *) data writeToURL:fileURL atomically:YES];

清理：

if (data) {
    CFRelease(data);
    data = NULL;
}

if (imageSource) {
    CFRelease(imageSource);
    imageSource = NULL;
}

if (imageDestination) {
    CFRelease(imageDestination);
    imageDestination = NULL;
}

return success;

希望这可以帮助。但我想为 H2C03 的非常有用的建议投票，这有助于达成这个解决方案。请帮助我该怎么做。谢谢。