updating to .png skips the 'XMP Toolkit' tag, but with .jpg images it is added.

[rempargo]

System:               OS X 10.8.4
ExifTool version: 9.40

I use Ruby Rmagick to generate some new .png and .jpg images.
after this i use exiftool to add a description to the image with the following commands
for png:

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exiftool -Description='My description' my_file.png
for jpg:

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exiftool -Description='My description' my_file.jpg

When I look into the files with:

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exiftool my_image.png
and

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exiftool my_image.jpg

I see that the updated .jpg file has the 'XMP Toolkit'  tag, but the updated .png file doesn't.

The original .jpg file doesn't contain 'XMP Toolkit' tag, it is added by exiftool, so I wonder why this is not done for the .png file.

I think this behaviour is the reason that Adobe inDesign can generate a 'Live Caption' link for .jpg image, but can't for the .png file, but that is just an assumption. I prefer to use .png because of the 'Lossless' behaviour.

Rempargo

[Phil Harvey]

Hi Rempargo,

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> exiftool -description=test a.jpg a.png
    2 image files updated

> exiftool -description -G1 a.jpg a.png
======== a.jpg
[XMP-dc]        Description                     : test
======== a.png
[PNG]           Description                     : test
    2 image files read

If you want to write XMP:Description to a PNG file, you must be more specific.  For PNG images, PNG:Description is the preferred location.

- Phil

Edit: Also, it has been observed that some Adobe products ignore XMP if it comes at the end of a PNG file, so you might want to add -api PNGEarlyXMP (case sensitive) to your command when writing. See the Known Problems for more details.

[rempargo]

Thanks Phil, for the explaination.

The correct tag is now created and it solves the problems in Adobe inDesign.

Rempargo