[Image-SIG] PIL DPI trouble - Solved

jcupitt at gmail.com jcupitt at gmail.com
Sat Sep 22 12:51:23 CEST 2007

On 9/21/07, Luca De Santis <lucadex at gmail.com> wrote:
> The JPEG standard doesn't cover a way to encode the resolution of a
> file but the JFIF extension does. For a quick and useful introduction
> to these concepts you can visit the Wikipedia page
> http://en.wikipedia.org/wiki/JFIF
> Here you can find a very useful table with the byte map of a JFIF file.

My understanding is that EXIF has now pretty much replaced the JFIF
resolution system.


I think most image processing systems use EXIF to put DPI information
into JPEG images. PIL will read EXIF tags from a JPEG image, but (as
far as I can see) will not write tags back again. Googling for "PIL
EXIF" seems uncertain anyway.


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