bugGNU Octave - Bugs: bug #58479, plottyy print out is different...


bug #58479: plottyy print out is different than onscreen appearance

Submitter:  Rik <rik5>
Submitted:  Mon 01 Jun 2020 10:14:44 PM UTC
Category:  Plotting with OpenGL Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Inaccurate Result
Status:  None Assigned to:  None
Originator Name:  Open/Closed:  * Open
Release:  * dev Operating System:  * GNU/Linux
Fixed Release:  None Planned Release:  None
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Tue 02 Jun 2020 05:34:57 PM UTC, comment #3: 

This is most probably a consequence of bug #45600: for display, we specify the characters size in pixels when it should be in points. So for screens with a resolution greater than 72 dpi, characters are down scaled on-screen but not in printout.

Actually, bug #45600 is on my top list of annoyance, and I recently tried to solve it (again) but it is very hard do properly: it is easy to fix the size of characters onscreen, but then you have to circumvent the fact that gl2ps interprets pixels as points...

I think the proper way out is to send scaled data to gl2ps using gl2psAddPolyPrimitive (undocumented, see [1]). This would also let us stop using the deprecated GL_FEEDBACK render mode (see [2] for motivations behind gl2psAddPolyPrimitive) and let us solve bug #48689.

For this to happen there is a lot of work though :-).

[1] https://gitlab.onelab.info/gl2ps/gl2ps/-/blob/master/gl2ps.h
[2] http://www.geuz.org/pipermail/gl2ps/2016/000424.html

Pantxo Diribarne <pantxo>
Group Member
Tue 02 Jun 2020 03:21:40 PM UTC, comment #2: 

Trying to get savannah to embed images in bug report.

File 1 is

File 2 is

Rik <rik5>
Group administrator
Tue 02 Jun 2020 03:20:28 PM UTC, comment #1: 

File 1 is demo1.onscreen.png

File 2 is demo1.png

Rik <rik5>
Group administrator
Mon 01 Jun 2020 10:14:44 PM UTC, original submission:  

Test code

demo plotyy 1

The onscreen printout looks different than the result obtained with

print demo1.png

The difference is most obvious with the "Axis 2" ylabel.

The file demo1.onscreen.png is a screen capture and demo1.png is the printout.

Rik <rik5>
Group administrator


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Attach Files:

Attached Files
file #49198:  demo1.onscreen.png added by rik5 (30KiB - image/png)
file #49199:  demo1.png added by rik5 (29KiB - image/png)


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    Follow 2 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2020-06-01 rik5 Attached File- Added demo1.onscreen.png, #49198
        Attached File- Added demo1.png, #49199

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