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copied!<p>The following blog post is where I got my answer when I had issues with modifying and saving Exif data Caffeinated Cocoa. This works on iOS.</p> <p>Here is my test code for writing Exif and GPS data. It pretty much a copy and paste of the code from the above blog. I am using this to write exif data to a captured image.</p> <pre><code>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); </code></pre>

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