[NTG-context] Rotating jpeg image gives weird output

Max Chernoff mseven at telus.net
Tue Jun 14 11:45:13 CEST 2022


> So, I've rotated the image, but now two things happen:
> 
> 1. there's a weird offset (the image is moved to the right)
>
> This seems to be somehow related to the particular file. With a different
> file that does not happen.

This can sometimes happen if the image has an embedded EXIF
"Orientation" tag and you're using a buggy viewer. Really old versions
of Firefox/pdf.js had this bug. If this is the case, you should be able
to reproduce it with the following bash commands:

     convert -size 64x256 canvas:grey -fill black -draw "circle 32,128 16,112" demo1.jpg
     exiftool -Orientation='Rotate 90 CW' demo1.jpg -o demo2.jpg

Then, include "demo1.jpg" and "demo2.jpg" in a ConTeXt file using
\externalfigure. Both pictures should display as circles; if you get
ovals, then it's definitely EXIF-related.

> 2. The output contains this line
> . location=local,global. location=local,global

Never seen this before, which makes me suspect that maybe this isn't
EXIF-related. Maybe the image is just subtly corrupted?

Anyways, if the problem is EXIF-related, then opening and saving the image
file with MS Paint (or any other non-EXIF-aware editor) should fix things.
Otherwise, I have no suggestions.

-- Max


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