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Image-ExifTool
Posted on 2006-01-06 17:55:26-08 by themonk
PhotoShop Resolution
Hello

Is it possible to make the PhotoShop resolution block (ResolutionInfo / 3ED) writable so that
I can explictly set the value of the PhotoShop Resolution to a specific value ?

Currently this is set as READ ONLY...

I can extract it using the command line tool as follows

... exiftool -g -Photoshop:XResolution file.jpg

but I cannot do

... exiftool -g -Photoshop:XResolution=150 file.jpg

When I specify

... exiftool -XResolution=150 file.jpg

This appears to set the Resolution in the EXIF block but PhotoShop ignores that if a
PhotoShop Resolution (3ed) is defined...

I'm trying to ensure consistency between the resolutions stored in an image.
Some of our apps use the PhotoShop resolution, some do not, this is not a problem as long
as all the resolutions are set the same. If I set the Resolution in the EXIF block (as above) and
somebody then opens the file in PhotoShop the resolution maybe different.


I've tried tweaking the PhotoShop.pm file by adding the Writable flag but no luck so far...
It says the 'Tag: 'Photoshop:XResolution' does not exist


Any suggestions ....??

(Thanks in advance)

Direct Responses: 1595 | Write a response
Posted on 2006-01-06 19:21:16-08 by exiftool in response to 1593
Re: PhotoShop Resolution
Hi,

It wasn't as simple as just making the tag writable, but it wasn't too difficult to add this ability. I have just released ExifTool version 5.90 (available now from my web site) with this feature added.

I hope this helps.

There is a third place where the resolution is stored though -- in the JFIF APP0 segment. Hopefully this won't cause problems, but if it does let me know. ExifTool currently doesn't write to this segment, so adding this ability would be a bit more work, but still not too much of a bother.
Direct Responses: 1599 | Write a response
Posted on 2006-01-09 11:09:55-08 by themonk in response to 1595
Re: PhotoShop Resolution
Excellent, thanks...

It will be interesting to look at the code changes to see how you did it ...

Certainly, would be useful if you could modify the JFIF header as well ...
This would enable me to normalise the resolution in all possible places
to ensure that there is no possible chance of an app seeing the image the wrong size...
Not a huge priority though....initially I will just normalise the 'other' resolution values to the current value of the JFIF header..

May I take this opportunity to say what an excellent piece of work this is...
It must of taken you quite some time to amass the specific knowledge of all the supported data

Direct Responses: 1607 | Write a response
Posted on 2006-01-09 19:31:50-08 by exiftool in response to 1599
Re: PhotoShop Resolution
Well, I had a bit of spare time, so...

ExifTool 5.93 (just released) has the ability to edit JFIF resolution information.

Thanks for your endorsement, it's nice to be appreciated.

Yes, it certainly has taken a long time to collect all of the information I have on various file formats (and even longer to reverse-engineer the formats for which I couldn't find specifications!). I now have quite a comprehensive suite of file specifications, plus sample images from well over 1000 different sources. I've often thought that I could save other people a lot of trouble by making these documents and samples publicly available, but unfortunately those darn copyright laws prevent me from doing this.
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