为图像设置 exif 数据时出现问题

Question

我在 iOS 4.1 中使用新的 ImageIO 框架。我使用以下方法成功检索了 exif 元数据：

CFDictionaryRef metadataDict = CMGetAttachment(sampleBuffer, kCGImagePropertyExifDictionary , NULL);

读出来，它似乎是有效的。将图像保存出来是可行的，但图像中永远没有任何 exif 数据。

    CGImageDestinationRef myImageDest = CGImageDestinationCreateWithURL((CFURLRef) docurl, kUTTypeJPEG, 1, NULL);

    // Add the image to the destination using previously saved options. 
    CGImageDestinationAddImage(myImageDest, iref, NULL);

    //add back exif
    NSDictionary *props = [NSDictionary dictionaryWithObjectsAndKeys:
                            [NSNumber numberWithFloat:.1], kCGImageDestinationLossyCompressionQuality,
                           metadataDict, kCGImagePropertyExifDictionary, //the exif metadata
                                                        nil];

                          //kCGImagePropertyExifAuxDictionary

    CGImageDestinationSetProperties(myImageDest, (CFDictionaryRef) props);

    // Finalize the image destination. 
    bool status = CGImageDestinationFinalize(myImageDest);

Answer 1

以下博客文章是我在修改和保存 Exif 数据 Caffeinated Cocoa 时遇到问题时得到答案的地方。这适用于 iOS。

这是我编写 Exif 和 GPS 数据的测试代码。它几乎是上述博客中代码的复制和粘贴。我正在使用它来将 exif 数据写入捕获的图像。

NSData *jpeg = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer] ;

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

    //get all the metadata in the image
    NSDictionary *metadata = (NSDictionary *) CGImageSourceCopyPropertiesAtIndex(source,0,NULL);

    //make the metadata dictionary mutable so we can add properties to it
    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


    [GPSDictionary setValue:[NSNumber numberWithFloat:_lat] forKey:(NSString*)kCGImagePropertyGPSLatitude];
    [GPSDictionary setValue:[NSNumber numberWithFloat:_lon] forKey:(NSString*)kCGImagePropertyGPSLongitude];
    [GPSDictionary setValue:lat_ref forKey:(NSString*)kCGImagePropertyGPSLatitudeRef];
    [GPSDictionary setValue:lon_ref forKey:(NSString*)kCGImagePropertyGPSLongitudeRef];
    [GPSDictionary setValue:[NSNumber numberWithFloat:_alt] forKey:(NSString*)kCGImagePropertyGPSAltitude];
    [GPSDictionary setValue:[NSNumber numberWithShort:alt_ref] forKey:(NSString*)kCGImagePropertyGPSAltitudeRef]; 
    [GPSDictionary setValue:[NSNumber numberWithFloat:_heading] forKey:(NSString*)kCGImagePropertyGPSImgDirection];
    [GPSDictionary setValue:[NSString stringWithFormat:@"%c",_headingRef] forKey:(NSString*)kCGImagePropertyGPSImgDirectionRef];

    [EXIFDictionary setValue:xml 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); //this is the type of image (e.g., public.jpeg)

    //this will be the data CGImageDestinationRef will write into
    NSMutableData *dest_data = [NSMutableData data];

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

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

    //add the image contained in the image source to the destination, overidding the old metadata with our modified metadata
    CGImageDestinationAddImageFromSource(destination,source,0, (CFDictionaryRef) metadataAsMutable);

    //tell the destination to write the image data and metadata into our data object.
    //It will return false if something goes wrong
    BOOL success = NO;
    success = CGImageDestinationFinalize(destination);

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

    //now we have the data ready to go, so do whatever you want with it
    //here we just write it to disk at the same path we were passed
    [dest_data writeToFile:file atomically:YES];

    //cleanup

    CFRelease(destination);
    CFRelease(source);

Answer 2

我尝试了史蒂夫的答案并且它有效，但我认为大图像的速度很慢，因为它会复制整个图像。

您可以使用 CMSetAttachments 直接在 CMSampleBuffer 上设置属性。只需在致电jpegStillImageNSDataRepresentation之前执行此操作即可

CFDictionaryRef metaDict = CMCopyDictionaryOfAttachments(NULL, imageSampleBuffer, kCMAttachmentMode_ShouldPropagate);
CFMutableDictionaryRef mutable = CFDictionaryCreateMutableCopy(NULL, 0, metaDict);

NSMutableDictionary * mutableGPS = [self getGPSDictionaryForLocation:self.myLocation];
CFDictionarySetValue(mutable, kCGImagePropertyGPSDictionary, mutableGPS);

// set the dictionary back to the buffer
CMSetAttachments(imageSampleBuffer, mutable, kCMAttachmentMode_ShouldPropagate);

getGPSDictionaryForLocation: 方法可以在这里找到：

Saving Geotag info with photo on iOS4.1

Answer 3

我创建了一个 MSMutableDictionary 类别来帮助将地理标记和其他元数据保存到图像中。在这里查看我的博文：

http://blog.codecropper.com/2011/05/adding-metadata-to-ios-images-the-easy-way/

Answer 4

[由于没有解释的反对票而重新访问此答案。]

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。

更新版本在这里：

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

我将那里的代码修改如下：

- (void) saveImage:(UIImage *)imageToSave withInfo:(NSDictionary *)info
{
    // Get the image metadata (EXIF & TIFF)
    NSMutableDictionary * imageMetadata = [[info objectForKey:UIImagePickerControllerMediaMetadata] mutableCopy];

    // add (fake) GPS data
    CLLocationCoordinate2D coordSF = CLLocationCoordinate2DMake(37.732711,-122.45224);

    // arbitrary altitude and accuracy
    double altitudeSF = 15.0;
    double accuracyHorizontal = 1.0;
    double accuracyVertical = 1.0;
    NSDate * nowDate = [NSDate date];
    // create CLLocation for image
    CLLocation * loc = [[CLLocation alloc] initWithCoordinate:coordSF altitude:altitudeSF horizontalAccuracy:accuracyHorizontal verticalAccuracy:accuracyVertical timestamp:nowDate];

    // this is in case we try to acquire actual location instead of faking it with the code right above
    if ( loc ) {
        [imageMetadata setObject:[self gpsDictionaryForLocation:loc] forKey:(NSString*)kCGImagePropertyGPSDictionary];
    }

    // Get the assets library
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];

    // create a completion block for when we process the image
   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, using the completion block defined just above
    [library writeImageToSavedPhotosAlbum:[imageToSave CGImage]
                                 metadata:imageMetadata
                          completionBlock:imageWriteCompletionBlock];
}

我是从

imagePickerController:didFinishPickingMediaWithInfo:

这是图像选择器的委托方法。 （这就是我放置逻辑的地方，看看是否有要保存的图像等）

为了完整起见，这里是获取 GPS 数据作为字典的辅助方法：

- (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];

    // requires ImageIO
    [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;

}

另见Write UIImage along with metadata (EXIF, GPS, TIFF) in iPhone's Photo library

Answer 5

一篇文章涉及为 EXIF 数据创建 GPS 元数据字典。这是一个 CLLocation 类别可以做到这一点：

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

Answer 6

因为我还在学习，所以我花了一些时间来拼凑史蒂夫和马蒂的答案，以将元数据添加到图像的数据并随后保存它。下面，我对他们的答案做了一个不使用 ImageIO 方法的 Swift 实现。

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（也是 Swift）。

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
}

此时，您可以将图像数据写入文件或使用 Photos API 将图像保存到相机胶卷（对于 iOS 9+ 使用 PHAssetCreationRequest's addResource:with:data:options，或者对于较旧的 iOS 版本，通过将 imageData 写入临时文件，然后调用PHAssetChangeRequest.creationRequestForAssetFromImage:atFileURL)。请注意，iOS 9 不推荐使用 ALAssertLibrary。我在答案 here 中提供了更多实现细节。

Answer 7

这样我设置了EXIF数据，如果需要你也可以压缩照片，这解决了我的问题：希望它有帮助

// Get your image.
NSURL *url = @"http://somewebsite.com/path/to/some/image.jpg";
UIImage *loImgPhoto = [NSData dataWithContentsOfURL:url];

// Get your metadata (includes the EXIF data).
CGImageSourceRef loImageOriginalSource = CGImageSourceCreateWithData(( CFDataRef) loDataFotoOriginal, NULL);
NSDictionary *loDicMetadata = (__bridge NSDictionary *) CGImageSourceCopyPropertiesAtIndex(loImageOriginalSource, 0, NULL);

// Set your compression quality (0.0 to 1.0).
NSMutableDictionary *loDicMutableMetadata = [loDicMetadata mutableCopy];
[loDicMutableMetadata setObject:@(lfCompressionQualityValue) forKey:(__bridge NSString *)kCGImageDestinationLossyCompressionQuality];

// Create an image destination.
NSMutableData *loNewImageDataWithExif = [NSMutableData data];
CGImageDestinationRef loImgDestination = CGImageDestinationCreateWithData((__bridge CFMutableDataRef)loNewImageDataWithExif, CGImageSourceGetType(loImageOriginalSource), 1, NULL);


// Add your image to the destination.
CGImageDestinationAddImage(loImgDestination, loImgPhoto.CGImage, (__bridge CFDictionaryRef) loDicMutableMetadata);

// Finalize the destination.
if (CGImageDestinationFinalize(loImgDestination))
   {
       NSLog(@"Successful image creation.");                   
       // process the image rendering, adjustment data creation and finalize the asset edit.


       //Upload photo with EXIF metadata
       [self myUploadMethod:loNewImageDataWithExif];

    }
    else
    {
          NSLog(@"Error -> failed to finalize the image.");                         
    }

CFRelease(loImageOriginalSource);
CFRelease(loImgDestination);

Answer 8

SWIFT 5：

我花了一周的时间来确定范围，将所有部分收集到工作代码中。

这会将UIImage 保存为带有 GPS 元数据的 JPEG 临时文件：

let image:UIImage = mImageView.image! // your UIImage

// create filename
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy.MM.dd-HH.mm.ss"
let now = Date()
let date_time = dateFormatter.string(from: now)
let fileName:String = "your_image_"+date_time+".jpg" // name your file the way you want
let temporaryFolder:URL = FileManager.default.temporaryDirectory
let temporaryFileURL:URL = temporaryFolder.appendingPathComponent(fileName)

// save the image to chosen path
let jpeg = image.jpegData(compressionQuality: 0.85)! // set JPG quality here (1.0 is best)
let src = CGImageSourceCreateWithData(jpeg as CFData, nil)!
let uti = CGImageSourceGetType(src)!
let cfPath = CFURLCreateWithFileSystemPath(nil, temporaryFileURL.path as CFString, CFURLPathStyle.cfurlposixPathStyle, false)
let dest = CGImageDestinationCreateWithURL(cfPath!, uti, 1, nil)

// create GPS metadata from current location
let gpsMeta = gCurrentLocation?.exifMetadata() // gCurrentLocation is your CLLocation (exifMetadata is an extension)
let tiffProperties = [
    kCGImagePropertyTIFFMake as String: "Camera vendor",
    kCGImagePropertyTIFFModel as String: "Camera model"
    // --(insert other properties here if required)--
] as CFDictionary

let properties = [
    kCGImagePropertyTIFFDictionary as String: tiffProperties,
    kCGImagePropertyGPSDictionary: gpsMeta as Any
    // --(insert other dictionaries here if required)--
] as CFDictionary  

CGImageDestinationAddImageFromSource(dest!, src, 0, properties)
if (CGImageDestinationFinalize(dest!)) {
    print("Saved image with metadata!")
} else {
    print("Error saving image with metadata")
}

这是 GPS 元数据扩展 （来自https://gist.github.com/chefren/8b50652d67c397a825619f83c8dba6d3）：

import Foundation
import CoreLocation

extension CLLocation {

    func exifMetadata(heading:CLHeading? = nil) -> NSMutableDictionary {

        let GPSMetadata = NSMutableDictionary()
        let altitudeRef = Int(self.altitude < 0.0 ? 1 : 0)
        let latitudeRef = self.coordinate.latitude < 0.0 ? "S" : "N"
        let longitudeRef = self.coordinate.longitude < 0.0 ? "W" : "E"

        // GPS metadata
        GPSMetadata[(kCGImagePropertyGPSLatitude as String)] = abs(self.coordinate.latitude)
        GPSMetadata[(kCGImagePropertyGPSLongitude as String)] = abs(self.coordinate.longitude)
        GPSMetadata[(kCGImagePropertyGPSLatitudeRef as String)] = latitudeRef
        GPSMetadata[(kCGImagePropertyGPSLongitudeRef as String)] = longitudeRef
        GPSMetadata[(kCGImagePropertyGPSAltitude as String)] = Int(abs(self.altitude))
        GPSMetadata[(kCGImagePropertyGPSAltitudeRef as String)] = altitudeRef
        GPSMetadata[(kCGImagePropertyGPSTimeStamp as String)] = self.timestamp.isoTime()
        GPSMetadata[(kCGImagePropertyGPSDateStamp as String)] = self.timestamp.isoDate()
        GPSMetadata[(kCGImagePropertyGPSVersion as String)] = "2.2.0.0"

        if let heading = heading {
            GPSMetadata[(kCGImagePropertyGPSImgDirection as String)] = heading.trueHeading
            GPSMetadata[(kCGImagePropertyGPSImgDirectionRef as String)] = "T"
        }

        return GPSMetadata
    }
}

extension Date {

    func isoDate() -> String {
        let f = DateFormatter()
        f.timeZone = TimeZone(abbreviation: "UTC")
        f.dateFormat = "yyyy:MM:dd"
        return f.string(from: self)
    }

    func isoTime() -> String {
        let f = DateFormatter()
        f.timeZone = TimeZone(abbreviation: "UTC")
        f.dateFormat = "HH:mm:ss.SSSSSS"
        return f.string(from: self)
    }
}

就是这样！

您现在可以使用activityViewController 将临时图像（使用temporaryFileURL）保存到相册，或将其保存为文件，或将其共享到其他应用程序，或任何您想要的。

Answer 9

将 Steve McFarlin 的 answer 翻译成 Swift 并将其封装在一个类中。

class GeoTagImage {

  /// Writes GPS data into the meta data.
  /// - Parameters:
  ///   - data: Coordinate meta data will be written to the copy of this data.
  ///   - coordinate: Cooordinates to write to meta data.
  static func mark(_ data: Data, with coordinate: Coordinate) -> Data {
    var source: CGImageSource? = nil
    source = CGImageSourceCreateWithData((data as CFData?)!, nil)
    // Get all the metadata in the image
    let metadata = CGImageSourceCopyPropertiesAtIndex(source!, 0, nil) as? [AnyHashable: Any]
    // Make the metadata dictionary mutable so we can add properties to it
    var metadataAsMutable = metadata
    var EXIFDictionary = (metadataAsMutable?[(kCGImagePropertyExifDictionary as String)]) as? [AnyHashable: Any]
    var GPSDictionary = (metadataAsMutable?[(kCGImagePropertyGPSDictionary as String)]) as? [AnyHashable: Any]

    if !(EXIFDictionary != nil) {
      // If the image does not have an EXIF dictionary (not all images do), then create one.
      EXIFDictionary = [:]
    }
    if !(GPSDictionary != nil) {
      GPSDictionary = [:]
    }

    // add coordinates in the GPS Dictionary
    GPSDictionary![(kCGImagePropertyGPSLatitude as String)] = coordinate.latitude
    GPSDictionary![(kCGImagePropertyGPSLongitude as String)] = coordinate.longitude
    EXIFDictionary![(kCGImagePropertyExifUserComment as String)] = "Raw Image"

    // Add our modified EXIF data back into the image’s metadata
    metadataAsMutable!.updateValue(GPSDictionary!, forKey: kCGImagePropertyGPSDictionary)
    metadataAsMutable!.updateValue(EXIFDictionary!, forKey: kCGImagePropertyExifDictionary)

    // This is the type of image (e.g., public.jpeg)
    let UTI: CFString = CGImageSourceGetType(source!)!

    // This will be the data CGImageDestinationRef will write into
    let dest_data = NSMutableData()
    let destination: CGImageDestination = CGImageDestinationCreateWithData(dest_data as CFMutableData, UTI, 1, nil)!
    // Add the image contained in the image source to the destination, overidding the old metadata with our modified metadata
    CGImageDestinationAddImageFromSource(destination, source!, 0, (metadataAsMutable as CFDictionary?))

    // Tells the destination to write the image data and metadata into our data object.
    // It will return false if something goes wrong
    _ = CGImageDestinationFinalize(destination)

    return (dest_data as Data)
  }

  /// Prints the Meta Data from the Data.
  /// - Parameter data: Meta data will be printed of this object.
  static func logMetaData(from data: Data) {
    if let imageSource = CGImageSourceCreateWithData(data as CFData, nil) {
      let imageProperties = CGImageSourceCopyPropertiesAtIndex(imageSource, 0, nil)
      if let dict = imageProperties as? [String: Any] {
        print(dict)
      }
    }
  }
}