我正在开发一个项目，其要求是： - 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。 我已经浏览了一些论坛。我试着编写这个逻辑。我想，我已达到目的，但由于我无法看到我附加到图像的元数据，因此缺少了一些东西。 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);
}
请帮助我做这件事并获得积极的一面。 看看最后一行，我是否用我的元数据保存了图像？ 图像将在此时保存，但我附加到的元数据不会被保存。
提前致谢。
答案 0 :(得分：13)
Apple更新了他们解决此问题的文章（Technical Q＆amp; A QA1622）。如果您使用的是较旧版本的Xcode，您可能仍会有文章说或多或少，运气不好，如果不对图像数据进行低级解析，则无法执行此操作。
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 = <•••>; // 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];
}
我从
打电话给我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，这对我在iOS4和iOS5设备上运行良好。
更新：和iOS6 / iOS7设备。我使用这段代码构建了一个简单的项目：
答案 1 :(得分：7)
功能：UIImageWriteToSavePhotosAlbum仅写入图像数据。
您需要阅读ALAssetsLibrary
您最终要调用的方法是：
ALAssetsLibrary *library = [[ALAssetsLibrary alloc]
[library writeImageToSavedPhotosAlbum:metadata:completionBlock];
答案 2 :(得分：4)
对于那些来到这里试图用相机在你的应用程序中拍照并将图像文件保存到带GPS元数据的相机胶卷的人来说，我有一个 Swift解决方案使用{{3自iOS 9.0以来 Photos API已弃用。
正如rickster对此ALAssetsLibrary所述，即使您设置了新资产的.location属性，照片API也会不将位置数据直接嵌入到JPG图像文件中。 / p>
给定一个CMSampleBuffer示例缓冲区buffer，一些CLLocation location，并使用Morty的answer来使用CMSetAttachments以避免重复图像，我们可以执行以下操作。可以找到扩展CLLocation的gpsMetadata方法suggestion。
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。如果您支持较早的iOS并且想要使用Photos API，那么您必须创建一个临时文件，然后从该URL的文件创建资产如果您想正确嵌入GPS元数据（PHAssetChangeRequest.creationRequestForAssetFromImage:atFileURL）。仅设置PHAsset的.location不会将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?()
}
})
}
除了： 如果您只想将带有GPS元数据的图像保存到临时文件或文档（而不是相机胶卷/照片库），则可以跳过使用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
}
答案 3 :(得分：2)
其中一部分涉及生成GPS元数据。这是CLLocation上的一个类别：
答案 4 :(得分：2)
从应用程序中的凸轮捕获图像获取元数据：
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];
或想要保存到本地目录
CGImageDestinationAddImageFromSource(destinationPath,sourceImage,0, (CFDictionaryRef)imageMetadata);
答案 5 :(得分：1)
我们要解决的问题是：用户刚刚使用UIImagePickerController相机拍照。我们得到的是UIImage。当我们将元数据保存到相机胶卷（照片库）时，我们如何将元数据折叠到UIImage中，现在我们还没有AssetsLibrary框架？
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。
在此示例中，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)
})
测试的一个好方法 - 以及一个常见的用例 - 是通过info键从UIImagePickerController委托UIImagePickerControllerMediaMetadata字典接收照片元数据，并将其折叠到PHAsset中，因为我们将其保存到照片库。
答案 6 :(得分：1)
有许多框架处理图像和元数据。
不推荐使用Assets Framework，并将其替换为Photos Library框架。如果您实施AVCapturePhotoCaptureDelegate来捕获照片，则可以执行此操作：
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)
...
}
元数据是字典词典，您必须参考CGImageProperties。
我写了关于这个话题here。
答案 7 :(得分：0)
这里的@matt答案略有不同。
以下代码仅使用一个CGImageDestination，更有趣的是允许在iOS11 +上以HEIC格式保存。
请注意，在添加图像之前，已将压缩质量添加到元数据。 0.8大约是本机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