iphone - 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的图像的元数据中。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？那时图像正在被保存，但我附加到它的元数据没有被保存。

提前致谢。

score 13 · Accepted Answer

Apple 更新了他们的文章来解决这个问题（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

我在那里修改了代码如下：

- (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 = <•••&gt;; // 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];
}

我称之为

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

score 6 · Accepted Answer

功能：UIImageWriteToSavePhotosAlbum 只写入图像数据。

您需要阅读ALAssetsLibrary

您最终要调用的方法是：

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

score 5 · Accepted Answer

对于任何来这里尝试在您的应用程序中使用相机拍照并将图像文件保存到带有 GPS 元数据的相机胶卷的人，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 在这个答案中提到的那样，即使您设置了新资产的 .location 属性，Photos API 也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 的建议以CMSetAttachments避免重复图像，我们可以执行以下操作。gpsMetadata可以在这里找到扩展 CLLocation的方法。

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，这种方便的addResource:with:data:options方法仅在 iOS 9 中可用。如果您支持早期的 iOS 并希望使用 Photos API，那么您必须创建一个临时文件，然后在该 URL 的文件中创建一个资产（如果您想拥有） GPS 元数据正确嵌入 ( 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?()
      }
    })
  }

另外：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
}

score 2 · Accepted Answer

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

score 2 · Accepted Answer

在应用程序中从 cam 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);

score 1 · Accepted Answer

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。

在这个例子中，im是 UIImage 并且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——是通过密钥从 UIImagePickerController 委托info字典接收照片元数据，UIImagePickerControllerMediaMetadata并将其折叠到 PHAsset 中，同时将其保存到照片库中。

score 1 · Accepted Answer

有许多处理图像和元数据的框架。

资产框架已弃用，取而代之的是照片库框架。如果你实现AVCapturePhotoCaptureDelegate了捕捉照片，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。

我在这里写过这个话题。

score 1 · Accepted Answer

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，压缩质量是在添加图像之前添加到元数据中的。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

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

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