使用新的PHPhotoLibrary保存exif元数据 [英] Save the exif metadata using the new PHPhotoLibrary

问题描述

我目前正在使用 AVCaptureStillImageOutput 来获取完整分辨率图片。我还可以使用以下代码获取exif元数据：

I am currently using AVCaptureStillImageOutput to get a full resolution picture. I am also able to get the exif metadata using the following code:

[self.stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error)
     { 

         CFDictionaryRef metaDict = CMCopyDictionaryOfAttachments(NULL, imageSampleBuffer, kCMAttachmentMode_ShouldPropagate);
         CFMutableDictionaryRef mutableDict = CFDictionaryCreateMutableCopy(NULL, 0, metaDict);

         NSLog(@"test attachments %@", mutableDict);

         // set the dictionary back to the buffer
         CMSetAttachments(imageSampleBuffer, mutableDict, kCMAttachmentMode_ShouldPropagate);

         NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer];

         UIImage *image = [[UIImage alloc] initWithData:imageData];    
         [self.delegate frameReadyToSave:image withExifAttachments: mutableDict];
     }];

元数据位于 mutableDict 变量中。现在，我想用两个元数据将这张图片保存在两个不同的地方。我想将它保存在应用程序文件夹和照片库中的磁盘上。

The metadata being located in the mutableDict variable. Now, I want to save this picture in two different places, with the metadata. I want to save it on the disk in the application folders and in the Photo Library.

现在，我尝试使用以下方法以另一种方法保存图像（您看到的图像变量是自定义对象）：

Now, I tried to save the image, in another method, using the following (the image variable you see is a custom object):

NSData* imageData = UIImageJPEGRepresentation(image.image, 1.0f);

[imageData writeToFile:image.filePath atomically:YES];

UIImageWriteToSavedPhotosAlbum(image.image, nil, nil, nil);

现在，图像已正确保存，但不包含任何Exif元数据。

Now, the image is properly saved but does not contain any Exif metadata.

从我读过的内容来看，我需要使用PHPhotoLibrary这样做，但文档并不是那么啰嗦。这是我找到的：

From what I have read, I need to use the PHPhotoLibrary to do so but the documentation isn't too loquacious on that. Here's what I found:

[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
    PHAssetChangeRequest *createAssetRequest = [PHAssetChangeRequest creationRequestForAssetFromImage:image.image];      

} completionHandler:nil];

但如何用它保存元数据？

But how do I save the metadata with it?

推荐答案

我建议您使用ImageIO来实现：

I would suggest you use ImageIO to accomplish that:

-(void)frameReadyToSave:(UIImage*)image withExifAttachments:(NSMutableDictionary*)mutableDict
{
    NSData* imageData = UIImageJPEGRepresentation(image, 1.0f);
    CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef) imageData, NULL);
    __block NSURL* tmpURL = [NSURL fileURLWithPath:@"example.jpg"]; //modify to your needs
    CGImageDestinationRef destination = CGImageDestinationCreateWithURL((__bridge CFURLRef) tmpURL, kUTTypeJPEG, 1, NULL);
    CGImageDestinationAddImageFromSource(destination, source, 0, (__bridge CFDictionaryRef) mutableDict);
    CGImageDestinationFinalize(destination);
    CFRelease(source);
    CFRelease(destination);
    [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
        [PHAssetChangeRequest creationRequestForAssetFromImageAtFileURL:tmpURL];
    }   completionHandler:^(BOOL success, NSError *error) {
        //cleanup the tmp file after import, if needed
    }];
}

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