[kwlug-disc] Image Comparison

Chris Irwin chris at chrisirwin.ca
Fri Aug 14 15:05:16 EDT 2009

On Fri, 2009-08-14 at 11:20 -0400, Khalid Baheyeldin wrote:

> You cannot rely on the EXIF info being carried forward in derivative
> images as is.
> I think the EXIF info gets removed if you resize, crop, ...etc.

EXIF information CAN be carried over to derivative images, but the
editor you are using must be aware of it. If you're using something
extremely simple to resize (eg. ms paint, like a friend of mine), it
doesn't understand EXIF and will ignore it. Upon saving the image, it
won't bother writing out the "garbage" data it didn't understand from
the original document.

If you use the gimp, you should be fine. Most photo-management apps
should be good.

Some cameras put rotation information in EXIF to inform the viewer that
the photo should be rotated 90 degrees. I'm not sure how this gets
handled on re-saving...

Chris Irwin <chris at chrisirwin.ca>
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