bugGNU Octave - Bugs: bug #65959, qt backend: should print with...


bug #65959: qt backend: should print with -rNUM set dpi related metadata for png, jpeg, etc.?

Submitter:  b3nmore <b3nmore>
Submitted:  Sat 06 Jul 2024 09:09:53 AM UTC
Category:  Plotting Severity:  3 - Normal
Priority:  5 - Normal Item Group:  None
Status:  None Assigned to:  None
Originator Name:  Open/Closed:  * Open
Release:  * 9.2.0 Operating System:  * Any
Fixed Release:  None Planned Release:  None
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Sat 06 Jul 2024 09:09:53 AM UTC, original submission:  

I recently switched from the fltk to the qt graphics-toolkit and noticed, that the dpi related metadata is handled quite differently when printing to jpeg/png files with the resolution option "-rNUM".

Here are may findings:

  • the image size is calculated correctly by both backends
  • fltk backend: 'X Resolution'/'Y Resolution' (jpeg) and 'Pixels Per Unit X/Y', 'Pixel Units' (png) are set correctly
  • qt backend: jpeg: 'X Resolution'/'Y Resolutions' is always set to 72 dpi. png: no dpi related metadata is written at all

Not sure what would be the right approach (setting dpi related metadata explicitly or omitting it), but imo it should be handled consistently for all raster image files (at least where applicable).


b3nmore <b3nmore>


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