如何在编辑PHAsset时保留原始照片元数据？ [英] How to preserve original photo metadata when editing PHAssets?

问题描述

我正在通过PhotoKit编辑照片，但我发现这不能保存原始照片的元数据。即使是苹果公司提供的SamplePhotosApp，当他们应用深褐色或Chrome滤镜时，也会发生这种情况。我的问题是，您如何确保保留所有原始照片元数据？

我已经了解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我创建的最终CIImage，但在提交编辑时它仍然被删除。将CIImage转换为CGImage到UIImage到NSData的方式或将其写入磁盘的方式肯定有问题。

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：

推荐答案

根据苹果的CIImage.Properties文档：

如果CIImage对象是筛选器(或筛选器链)的输出，则此方法返回筛选器的原始输入图像中的元数据。

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的内容读取为NSData

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，则不需要将CFDataRef强制转换为NSD字典*，但我这样做只是为了完整性。

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