Codecov Report

Patch coverage: 71.42% and project coverage change: -1.46 ⚠️

Comparison is base (b0f3206) 72.20% compared to head (57416ff) 70.75%.

@@            Coverage Diff             @@
##           master     #246      +/-   ##
==========================================
- Coverage   72.20%   70.75%   -1.46%     
==========================================
  Files          34       34              
  Lines        9023     9036      +13     
==========================================
- Hits         6515     6393     -122     
- Misses       2508     2643     +135     

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I've tried this on my non-highres Linux laptop. It certainly changes something. If I export a scatterplot as a PNG with the old code I see the following with identify -verbose -units PixelsPerInch file.png

Geometry: 805x663+0+0
Resolution: 96.01x96.01
Print size: 8.38454x6.90553

And with the new code:

Geometry: 805x663+0+0
Resolution: 72.01x72.01
Print size: 11.179x9.20705

So the new code behaves as specified, but is it really correct? It seems that resolutions was already set properly before. Can you share similar info from a PNG exported on a retina Mac?

Otherwise this code does not break anything for me, a non-retina user.

I get 144x144, as I should.

I don't know where your 96 came from. Now that it is changed to 72, some programs might show it larger then before. But to my experience, most either ignore it (e.g. browsers) or it doesn't matter (e.g. Word, Powerpoint, where the user resizes the image anyway).

With this PR I understand that we get either 72 or 144. But I saw that dpi was saved correctly before on my computer (it is set to 96 dpi), so I wonder if it was also saved correctly on your Mac on master. If it is, I'd remove the dpi-setting code from the png exporter.

For me, it was always 72. Now, with 144, the saved image has the same size as the original in the widget.

I would think that using devicePixelRatio should result in the appropriate image size, because Qt uses this same scaling factor internally. If your correct dpi is 96, than devicePixelRatio should be returning 1.33?

Could you please investigate this? We need to fix this and I don't have a suitable machine to try it on.

Sure, I'll look into this.