I have a php script which uses the Flickr API to download my images from Flickr, parse the associated text and metadata, and save versions on my server with the metadata embedded in the image files. I work with historic images and want to display them in date order on my smartphone (I'm trying out F-Stop app on Android).
I've got the metadata update working using the PHP JPEG Metadata Toolkit - http://www.ozhiker.com/electronics/pjmt/ - by writing XMP data to the files. But for the life of me I can't seem to get the 'date taken' working!
Here are some sample images:
This is the original file from Flickr, with the date set as the date I created the file http://metapicz.com/#landing?imgsrc=http%3A%2F%2Fwww.whatsthatpicture.com%2Ftools%2FPHP_JPEG_Metadata_Toolkit%2Fflickr.jpg (right-click on the image and save it if you want to inspect it locally)
Here's my first attempt with the toolkit. It has updated the XMP 'DateCreated' but not the EXIF CreateDate or XMP CreateDate http://metapicz.com/#landing?imgsrc=http%3A%2F%2Fwww.whatsthatpicture.com%2Ftools%2FPHP_JPEG_Metadata_Toolkit%2Fprocessed_orig.jpg
So I then forced it to change the XMP CreateDate http://metapicz.com/#landing?imgsrc=http%3A%2F%2Fwww.whatsthatpicture.com%2Ftools%2FPHP_JPEG_Metadata_Toolkit%2Fprocessed_new.jpg. This then showed up in Windows Explorer as the date created, but not in the F-Stop app.
So I was wondering if the EXIF CreateDate, which is still at the value from Flickr, was taking precedence so I stripped that metadata out (the toolset doesn't allow you to modify EXIF, as far as I can see) http://metapicz.com/#landing?imgsrc=http%3A%2F%2Fwww.whatsthatpicture.com%2Ftools%2FPHP_JPEG_Metadata_Toolkit%2Fprocessed_new2.jpg
In none of these cases does F-Stop interpret the date correctly. I have contacted the devs but I don't actually think it's the app at fault, I think it's the metadata format in the files. That's because when I displayed that original file in Windows Explorer and changed the Date Taken there, this file works perfectly http://metapicz.com/#landing?imgsrc=http%3A%2F%2Fwww.whatsthatpicture.com%2Ftools%2FPHP_JPEG_Metadata_Toolkit%2Fflickr_win.jpg
Can anyone tell what is going on, or suggest another way I might go about this?
OK, I've now solved this.
It seems that the FStop app can't read dates from the xmp files so it was either reading them from the JFIF/App12/"Ducky" segment at the beginning of the file, or if that didn't exist it was reading the file timestamp. Of course that meant my plan to create a single xmp profile with all my metadata wasn't going to work.
I switched to ImageMagick but that faced the same problem - I could strip profiles and load/change an xmp profile but couldn't immediately see a way to get it to create/update the date values in the JFIF segment.
So in the end I resorted to calling exiftool via an exec command exec("exiftool -AllDates='1863-07-23 12:00:00' -overwrite_original testfile.jpg"); (I'll change it away from AllDates and just set CreateDate, but I need to test that)
A bit clunky, but it works! I'm using Imagick anyway for modifying the actual images, so if anyone does know a way I might modify those headers there then I'd be delighted to hear it.