PHPhotoLibrary error while saving image at url

问题

I create an image at url provided by PHContentEditingOutput. When I load data to UIImage and save it like this - it works.

[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
    NSData *data = [NSData dataWithContentsOfURL:contentEditingOutput.renderedContentURL]
    UIImage *image = [UIImage imageWithData:data];
    [PHAssetChangeRequest creationRequestForAssetFromImage:image];
} completionHandler:^(BOOL success, NSError *error) {
     ...
}];

But when I try approach with url it fails:

[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
    [PHAssetChangeRequest creationRequestForAssetFromImageAtFileURL:contentEditingOutput.renderedContentURL];
} completionHandler:^(BOOL success, NSError *error) {
     ...
}];

Error:

Error Domain=NSCocoaErrorDomain Code=-1 "The operation couldn’t be completed. (Cocoa error -1.)"

UPDATE:

The same error when I try to save a modification.

[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
    PHAssetChangeRequest *request = [PHAssetChangeRequest changeRequestForAsset:asset];
    request.contentEditingOutput = contentEditingOutput;
} completionHandler:^(BOOL success, NSError *error) {
     ...
}];

The method works for a video (creationRequestForAssetFromVideoAtFileURL:), but not for an image. What went wrong?

回答1:

The problem is in the file format. I was trying to edit PNG screenshot, but renderingContentURL was always tmp/filename.JPG. At first I thought it was a bug, but according to the documentation this is correct behaviour.

renderedContentURL

Read this property to find a URL for writing edited asset content. Then, if editing a photo asset, write the altered photo image to a file in JPEG format at this URL. If editing a video asset, export the video to a QuickTime (.mov) file at this URL.

The solution is to convert the image with function

NSData *UIImageJPEGRepresentation(UIImage *image, CGFloat compressionQuality);

回答2:

When passing the metadata, I also had the issue consistently showing whenever the Orientation (inside the image metadata) was anything other than CGImagePropertyOrientationUp.

This is also stated inside the renderedContentURL documentation:

Edited asset content must incorporate (or “bake in”) the intended orientation of the asset. That is, the orientation metadata (if any) that you write in the output image or video file must declare the “up” orientation, and the image or video data must appear right-side up when presented without orientation metadata.

For images, the following metadata keys need to be updated (while the image data is also rotated):
• kCGImagePropertyTIFFDictionary \ kCGImagePropertyTIFFOrientation
• kCGImagePropertyOrientation
• possibly, kCGImagePropertyIPTCImageOrientation

来源：https://stackoverflow.com/questions/28348450/phphotolibrary-error-while-saving-image-at-url