如何在编辑PHAssets时保留原始照片元数据？

Question

我正在通过PhotoKit编辑照片,但我发现这不会保留原始照片的元数据.即使Apple应用Sepia或Chrome过滤器时提供的SamplePhotosApp也会出现这种情况.我的问题是,您如何确保保留所有原始照片元数据？

我已经发现了如何获取原始图像的元数据,并且我能够将该元数据保存到CIImage我创建的最终元数据中,但是在提交编辑时它仍然被删除.我将转换CIImage为a CGImage转换为UIImageto NSData,或者我将其写入磁盘的方式一定存在问题.

asset.requestContentEditingInputWithOptions(options) { (input: PHContentEditingInput!, _) -> Void in
    //Get full image
    let url = input.fullSizeImageURL
    let orientation = self.input.fullSizeImageOrientation
    var inputImage = CIImage(contentsOfURL: url)
    inputImage = inputImage.imageByApplyingOrientation(orientation)

    //do some processing on original photo here and create a CGImage...

    //save the original photo's metadata to a new CIImage:
    let originalMetadata = inputImage.properties()
    let newImage = CIImage(CGImage: editedCGImage, options: [kCIImageProperties: originalMetadata])

    println(newImage.properties()) //correctly prints all metadata!

    //commit changes to disk - somewhere after this line the metadata is lost
    let eaglContext = EAGLContext(API: .OpenGLES2)
    let ciContext = CIContext(EAGLContext: eaglContext)
    let outputImageRef = ciContext.createCGImage(newImage, fromRect: newImage.extent())
    let uiImage = UIImage(CGImage: outputImageRef, scale: 1.0, orientation: UIImageOrientation.Up)
    let jpegNSData = UIImageJPEGRepresentation(uiImage, 0.75)

    let contentEditingOutput = PHContentEditingOutput(contentEditingInput: input)
    let success = jpegData.writeToURL(contentEditingOutput.renderedContentURL, options: NSDataWritingOptions.AtomicWrite, error: _)

    PHPhotoLibrary.sharedPhotoLibrary().performChanges({ () -> Void in
        let request = PHAssetChangeRequest(forAsset: asset)
        request.contentEditingOutput = contentEditingOutput
    }, completionHandler: { (success: Bool, error: NSError!) -> Void in
        if success == false { println('failed to commit image edit: \(error)') }
    })
})

原始 - 请注意GPS标签:

编辑照片后:

Answer 1

根据CIImage.properties的Apple文档:

如果CIImage对象是过滤器(或过滤器链)的输出,则此方法从过滤器的原始输入图像返回元数据.

话虽如此,如果文档不正确,我会这样做.

您需要自己保存属性.为此,您需要将URL的内容作为NSData读取

NSURL *url = @"http://somewebsite.com/path/to/some/image.jpg";
NSData *imageData = [NSData dataWithContentsOfURL:url];
CIImage *image = [CIImage imageWithData:imageData];

// Save off the properties
CGImageSourceRef imageSource = CGImageSourceCreateWithData((__bridge CFDataRef) imageData);
NSDictionary* metadata = (__bridge NSDictionary *) CGImageSourceCopyProperties(imageSource, NULL);

// process your image
// ...
NSData *outputData = // create data from altered image.

// Save the image
CGImageSourceRef outputImageSource = CGImageSourceCreateWithData((__bridge CFDataRef) outputData);
CFMutableDataRef jpegData = CFDataCreateMutable(NULL, 0);
CGImageDestinationRef outputDestination = CGImageDestinationCreateWithData(jpegData, CGImageSourceGetType(outputImageSource), 1, NULL);

// add the image data to the destination
CGImageDestinationAddImageFromSource(jpegData, outputImageSource, 0, (__bridge CFDictionaryRef) metadata);

if (CGImageDestinationFinalize(outputDestination)) {
    NSLog(@"Successful image creation.");
    // process the image rendering, adjustment data creation and finalize the asset edit.
} else {
    NSLog(@"Image creation failed.");
}

如果您不需要修改元数据,则无需将CFDataRef强制转换为NSDictionary*,但我这样做只是为了完整性.