Writing EXIF UserComment using Cocoa/CF
Writing EXIF UserComment using Cocoa/CF
- Subject: Writing EXIF UserComment using Cocoa/CF
- From: "Klaus L. Greulich" <email@hidden>
- Date: Tue, 28 Feb 2006 20:16:13 +0100
Hi!
My Problem is that I need to write some information in a jpeg file,
using the EXIF "UserComment" tag.
Reading Exif information is not the problem, it is simply done by:
mMetadata = (CFMutableDictionaryRef)CGImageSourceCopyPropertiesAtIndex
(source, 0, (CFDictionaryRef)options);
NSDictionary* exif = [(NSDictionary*)mMetadata objectForKey:@"{Exif}"];
(Thanks for the Sample Code "ImageApp" from Apple)
That gives me (printed via NSLog) the following:
[...]
DateTimeOriginal = "2006:02:26 11:13:17";
[...]
UserComment = " ";
[...]
Writing *some* information also seems not to be a problem, because:
NSMutableDictionary* newExif = [NSMutableDictionary
dictionaryWithDictionary:[newMetadata objectForKey:@"{Exif}"]];
[newExif setObject:@"2001:01:01 11:53:07" forKey:@"DateTimeOriginal"];
[newExif setObject:@"This is a test" forKey:@"UserComment"];
[newMetadata setObject:newExif forKey:@"{Exif}"];
CGImageDestinationCreateWithURL((CFURLRef)absURL, (CFStringRef)
typeName, 1, nil);
CGImageDestinationAddImage(dest, image, (CFDictionaryRef)newMetadata);
gives me:
[...]
DateTimeOriginal = "2001:01:01 11:53:07"; <-- That works, the entry
has been changed!
[...]
But there is no "UserComment" Tag ...
It is not only not changed, it is gone.
"UserComment" is the only tag I care about at the moment, because for
my project I need to write some information (Copyright, Information
about the image) in the jpeg file. :-(
Is that a known bug or did I something wrong? Changing
"DateTimeOriginal" worked without any problems ...
I know there are some third-party tools to write EXIF information,
but it would be much easier and elegant using Cocoa
(NSBitmapImageReps valueForProperty) or CoreFoundation for this task.
Perhaps someone has a solution ... ;-)
With best regards
Klaus L. Greulich
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