在 iPhone 的照片库中写入 UIImage 和元数据（EXIF、GPS、TIFF）

Question

我正在开发一个项目，其中的要求是： - 用户将通过应用程序打开相机 - 捕获图像后，一些数据将附加到捕获图像的元数据中。 我浏览了一些论坛。我试图编写这个逻辑。我想，我已经达到了这一点，但是由于我无法看到我附加到图像的元数据，所以缺少一些东西。 我的代码是：

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)image editingInfo:(NSDictionary *)dictionary 
{

    [picker dismissModalViewControllerAnimated:YES];

    NSData *dataOfImageFromGallery = UIImageJPEGRepresentation (image,0.5);
    NSLog(@"Image length:  %d", [dataOfImageFromGallery length]);


    CGImageSourceRef source;
    source = CGImageSourceCreateWithData((CFDataRef)dataOfImageFromGallery, NULL);

    NSDictionary *metadata = (NSDictionary *) CGImageSourceCopyPropertiesAtIndex(source, 0, NULL);

    NSMutableDictionary *metadataAsMutable = [[metadata mutableCopy]autorelease];
    [metadata release];

    NSMutableDictionary *EXIFDictionary = [[[metadataAsMutable objectForKey:(NSString *)kCGImagePropertyExifDictionary]mutableCopy]autorelease];
    NSMutableDictionary *GPSDictionary = [[[metadataAsMutable objectForKey:(NSString *)kCGImagePropertyGPSDictionary]mutableCopy]autorelease];


    if(!EXIFDictionary) 
    {
        //if the image does not have an EXIF dictionary (not all images do), then create one for us to use
        EXIFDictionary = [NSMutableDictionary dictionary];
    }

    if(!GPSDictionary) 
    {
        GPSDictionary = [NSMutableDictionary dictionary];
    }

    //Setup GPS dict - 
    //I am appending my custom data just to test the logic……..

    [GPSDictionary setValue:[NSNumber numberWithFloat:1.1] forKey:(NSString*)kCGImagePropertyGPSLatitude];
    [GPSDictionary setValue:[NSNumber numberWithFloat:2.2] forKey:(NSString*)kCGImagePropertyGPSLongitude];
    [GPSDictionary setValue:@"lat_ref" forKey:(NSString*)kCGImagePropertyGPSLatitudeRef];
    [GPSDictionary setValue:@"lon_ref" forKey:(NSString*)kCGImagePropertyGPSLongitudeRef];
    [GPSDictionary setValue:[NSNumber numberWithFloat:3.3] forKey:(NSString*)kCGImagePropertyGPSAltitude];
    [GPSDictionary setValue:[NSNumber numberWithShort:4.4] forKey:(NSString*)kCGImagePropertyGPSAltitudeRef]; 
    [GPSDictionary setValue:[NSNumber numberWithFloat:5.5] forKey:(NSString*)kCGImagePropertyGPSImgDirection];
    [GPSDictionary setValue:@"_headingRef" forKey:(NSString*)kCGImagePropertyGPSImgDirectionRef];

    [EXIFDictionary setValue:@"xml_user_comment" forKey:(NSString *)kCGImagePropertyExifUserComment];
    //add our modified EXIF data back into the image’s metadata
    [metadataAsMutable setObject:EXIFDictionary forKey:(NSString *)kCGImagePropertyExifDictionary];
    [metadataAsMutable setObject:GPSDictionary forKey:(NSString *)kCGImagePropertyGPSDictionary];

    CFStringRef UTI = CGImageSourceGetType(source);
    NSMutableData *dest_data = [NSMutableData data];

    CGImageDestinationRef destination = CGImageDestinationCreateWithData((CFMutableDataRef) dest_data, UTI, 1, NULL);

    if(!destination)
    {
        NSLog(@"--------- Could not create image destination---------");
    }


    CGImageDestinationAddImageFromSource(destination, source, 0, (CFDictionaryRef) metadataAsMutable);

    BOOL success = NO;
    success = CGImageDestinationFinalize(destination);

    if(!success)
    {
        NSLog(@"-------- could not create data from image destination----------");
    }

    UIImage * image1 = [[UIImage alloc] initWithData:dest_data];
    UIImageWriteToSavedPhotosAlbum (image1, self, nil, nil);    
}

请帮助我做到这一点，并得到一些积极的东西。 看看最后一行，我是否保存了包含元数据的图像？ 那时图像正在保存，但我附加到它的元数据没有保存。

提前致谢。

Answer 1

Apple 已更新其文章以解决此问题（技术问答 QA1622）。如果您使用的是旧版本的 Xcode，您可能仍然有文章说，或多或少，运气不好，如果不对图像数据进行低级解析，您将无法做到这一点。

https://developer.apple.com/library/ios/#qa/qa1622/_index.html

我对那里的代码进行了如下修改：

- (void) saveImage:(UIImage *)imageToSave withInfo:(NSDictionary *)info
{
    // Get the assets library
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];

    // Get the image metadata (EXIF & TIFF)
    NSMutableDictionary * imageMetadata = [[info objectForKey:UIImagePickerControllerMediaMetadata] mutableCopy];

    // add GPS data
    CLLocation * loc = <•••>; // need a location here
    if ( loc ) {
        [imageMetadata setObject:[self gpsDictionaryForLocation:loc] forKey:(NSString*)kCGImagePropertyGPSDictionary];
    }

    ALAssetsLibraryWriteImageCompletionBlock imageWriteCompletionBlock =
    ^(NSURL *newURL, NSError *error) {
        if (error) {
            NSLog( @"Error writing image with metadata to Photo Library: %@", error );
        } else {
            NSLog( @"Wrote image %@ with metadata %@ to Photo Library",newURL,imageMetadata);
        }
    };

    // Save the new image to the Camera Roll
    [library writeImageToSavedPhotosAlbum:[imageToSave CGImage] 
                                 metadata:imageMetadata 
                          completionBlock:imageWriteCompletionBlock];
    [imageMetadata release];
    [library release];
}

我是从

imagePickerController:didFinishPickingMediaWithInfo:

这是图像选择器的委托方法。

我使用辅助方法（改编自 GusUtils）从某个位置构建 GPS 元数据字典：

- (NSDictionary *) gpsDictionaryForLocation:(CLLocation *)location
{
    CLLocationDegrees exifLatitude  = location.coordinate.latitude;
    CLLocationDegrees exifLongitude = location.coordinate.longitude;

    NSString * latRef;
    NSString * longRef;
    if (exifLatitude < 0.0) {
        exifLatitude = exifLatitude * -1.0f;
        latRef = @"S";
    } else {
        latRef = @"N";
    }

    if (exifLongitude < 0.0) {
        exifLongitude = exifLongitude * -1.0f;
        longRef = @"W";
    } else {
        longRef = @"E";
    }

    NSMutableDictionary *locDict = [[NSMutableDictionary alloc] init];

    [locDict setObject:location.timestamp forKey:(NSString*)kCGImagePropertyGPSTimeStamp];
    [locDict setObject:latRef forKey:(NSString*)kCGImagePropertyGPSLatitudeRef];
    [locDict setObject:[NSNumber numberWithFloat:exifLatitude] forKey:(NSString *)kCGImagePropertyGPSLatitude];
    [locDict setObject:longRef forKey:(NSString*)kCGImagePropertyGPSLongitudeRef];
    [locDict setObject:[NSNumber numberWithFloat:exifLongitude] forKey:(NSString *)kCGImagePropertyGPSLongitude];
    [locDict setObject:[NSNumber numberWithFloat:location.horizontalAccuracy] forKey:(NSString*)kCGImagePropertyGPSDOP];
    [locDict setObject:[NSNumber numberWithFloat:location.altitude] forKey:(NSString*)kCGImagePropertyGPSAltitude];

    return [locDict autorelease];

}

到目前为止，这对我来说在 iOS4 和 iOS5 设备上运行良好。

更新：和 iOS6/iOS7 设备。我使用以下代码构建了一个简单的项目：

https://github.com/5teev/MetaPhotoSave

Answer 2

函数：UIImageWriteToSavePhotosAlbum只写入图像数据。

您需要阅读ALAssetsLibrary

你最终要调用的方法是：

 ALAssetsLibrary *library = [[ALAssetsLibrary alloc]
 [library writeImageToSavedPhotosAlbum:metadata:completionBlock];

Answer 3

对于任何来这里尝试在您的应用中使用相机拍照并将图像文件与 GPS 元数据一起保存到相机胶卷的人，我有一个使用 Photos API 的 Swift 解决方案因为 ALAssetsLibrary 自 iOS 9.0 起已弃用。

正如 rickster 在此 answer 中提到的，即使您设置了新资产的 .location 属性，Photos API不会将位置数据直接嵌入到 JPG 图像文件中。

给定一个CMSampleBuffer样本缓冲区buffer，一些CLLocationlocation，并使用Morty的suggestion来使用CMSetAttachments以避免重复图像，我们可以执行以下操作。扩展CLLocation的gpsMetadata方法可以在here找到。

if let location = location {
    // Get the existing metadata dictionary (if there is one)
    var metaDict = CMCopyDictionaryOfAttachments(nil, buffer, kCMAttachmentMode_ShouldPropagate) as? Dictionary<String, Any> ?? [:]

    // Append the GPS metadata to the existing metadata
    metaDict[kCGImagePropertyGPSDictionary as String] = location.gpsMetadata()

    // Save the new metadata back to the buffer without duplicating any data
    CMSetAttachments(buffer, metaDict as CFDictionary, kCMAttachmentMode_ShouldPropagate)
}

// Get JPG image Data from the buffer
guard let imageData = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(buffer) else {
    // There was a problem; handle it here
}

// Now save this image to the Camera Roll (will save with GPS metadata embedded in the file)
self.savePhoto(withData: imageData, completion: completion)

savePhoto 方法如下。请注意，方便的 addResource:with:data:options 方法仅在 iOS 9 中可用。如果您支持早期的 iO​​S 并希望使用 Photos API，那么您必须创建一个临时文件，然后从该 URL 的文件创建一个资产，如果您希望正确嵌入 GPS 元数据 (PHAssetChangeRequest.creationRequestForAssetFromImage:atFileURL)。仅设置 PHAsset 的 .location 不会将您的新元数据嵌入到实际文件本身中。

func savePhoto(withData data: Data, completion: (() -> Void)? = nil) {
    // Note that using the Photos API .location property on a request does NOT embed GPS metadata into the image file itself
    PHPhotoLibrary.shared().performChanges({
      if #available(iOS 9.0, *) {
        // For iOS 9+ we can skip the temporary file step and write the image data from the buffer directly to an asset
        let request = PHAssetCreationRequest.forAsset()
        request.addResource(with: PHAssetResourceType.photo, data: data, options: nil)
        request.creationDate = Date()
      } else {
        // Fallback on earlier versions; write a temporary file and then add this file to the Camera Roll using the Photos API
        let tmpURL = URL(fileURLWithPath: NSTemporaryDirectory(), isDirectory: true).appendingPathComponent("tempPhoto").appendingPathExtension("jpg")
        do {
          try data.write(to: tmpURL)

          let request = PHAssetChangeRequest.creationRequestForAssetFromImage(atFileURL: tmpURL)
          request?.creationDate = Date()
        } catch {
          // Error writing the data; photo is not appended to the camera roll
        }
      }
    }, completionHandler: { _ in
      DispatchQueue.main.async {
        completion?()
      }
    })
  }

除此之外： 如果您只是想将带有 GPS 元数据的图像保存到临时文件或文档中（而不是相机胶卷/照片库），您可以跳过使用 Photos API 并直接将 imageData 写入 URL。

// Write photo to temporary files with the GPS metadata embedded in the file
let tmpURL = URL(fileURLWithPath: NSTemporaryDirectory(), isDirectory: true).appendingPathComponent("tempPhoto").appendingPathExtension("jpg")
do {
    try data.write(to: tmpURL)

    // Do more work here...
} catch {
    // Error writing the data; handle it here
}

Answer 4

其中一部分涉及生成 GPS 元数据。这是 CLLocation 上的一个类别，可以做到这一点：

https://gist.github.com/phildow/6043486

Answer 5

在应用程序中从摄像头捕获的图像中获取元数据：

UIImage *pTakenImage= [info objectForKey:@"UIImagePickerControllerOriginalImage"];

NSMutableDictionary *imageMetadata = [[NSMutableDictionary alloc] initWithDictionary:[info objectForKey:UIImagePickerControllerMediaMetadata]];

现在使用提取的元数据将图像保存到库中：

ALAssetsLibrary* library = [[ALAssetsLibrary alloc] init];
[library writeImageToSavedPhotosAlbum:[sourceImage CGImage] metadata:imageMetadata completionBlock:Nil];
[library release];

或者想保存到本地目录

CGImageDestinationAddImageFromSource(destinationPath,sourceImage,0, (CFDictionaryRef)imageMetadata);

Answer 6

我们试图解决的问题是：用户刚刚用 UIImagePickerController 相机拍照。我们得到的是一个 UIImage。既然我们没有 AssetsLibrary 框架，我们如何在将元数据保存到相机胶卷（照片库）时将元数据折叠到 UIImage 中？

答案（据我所知）是：使用 ImageIO 框架。从 UIImage 中提取 JPEG 数据，将其用作源并将其和元数据字典写入目标，并将目标数据作为 PHAsset 保存到相机胶卷中。

在本例中，im 是 UIImage，meta 是元数据字典：

let jpeg = UIImageJPEGRepresentation(im, 1)!
let src = CGImageSourceCreateWithData(jpeg as CFData, nil)!
let data = NSMutableData()
let uti = CGImageSourceGetType(src)!
let dest = CGImageDestinationCreateWithData(data as CFMutableData, uti, 1, nil)!
CGImageDestinationAddImageFromSource(dest, src, 0, meta)
CGImageDestinationFinalize(dest)
let lib = PHPhotoLibrary.shared()
lib.performChanges({
    let req = PHAssetCreationRequest.forAsset()
    req.addResource(with: .photo, data: data as Data, options: nil)
})

一个很好的测试方法——也是一个常见的用例——是通过 UIImagePickerControllerMediaMetadata 键从 UIImagePickerController 委托 info 字典接收照片元数据，并将其折叠到 PHAsset 中，同时将其保存到照片库中。

Answer 7

有许多处理图像和元数据的框架。

Assets Framework 已弃用，取而代之的是 Photos Library 框架。如果你实现了AVCapturePhotoCaptureDelegate 来拍摄照片，你可以这样做：

func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) {
    var metadata = photo.metadata
    metadata[kCGImagePropertyGPSDictionary as String] = gpsMetadata
    photoData = photo.fileDataRepresentation(withReplacementMetadata: metadata,
      replacementEmbeddedThumbnailPhotoFormat: photo.embeddedThumbnailPhotoFormat,
      replacementEmbeddedThumbnailPixelBuffer: nil,
      replacementDepthData: photo.depthData)
    ...
}

元数据是字典的字典，你必须参考CGImageProperties。

我写过这个话题here。

Answer 8

这是@matt 答案的细微变化。

以下代码仅使用一个 CGImageDestination 并且更有趣的是允许在 iOS11+ 上以 HEIC 格式保存。

请注意，压缩质量会在添加图像之前添加到元数据中。 0.8大致是原生相机保存的压缩质量。

//img is the UIImage and metadata the metadata received from the picker
NSMutableDictionary *meta_plus = metadata.mutableCopy;
//with CGimage, one can set compression quality in metadata
meta_plus[(NSString *)kCGImageDestinationLossyCompressionQuality] = @(0.8);
NSMutableData *img_data = [NSMutableData new];
NSString *type;
if (@available(iOS 11.0, *)) type = AVFileTypeHEIC;
else type = @"public.jpeg";
CGImageDestinationRef dest = CGImageDestinationCreateWithData((__bridge CFMutableDataRef)img_data, (__bridge CFStringRef)type, 1, nil);
CGImageDestinationAddImage(dest, img.CGImage, (__bridge CFDictionaryRef)meta_plus);
CGImageDestinationFinalize(dest);
CFRelease(dest); //image is in img_data
//go for the PHLibrary change request