Fix CairoMakie heatmap cell sizes #3625
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The heatmap_interpolation.png reference image differs slightly, that's probably why the test failed. If you tell me where to find the code generating the reference output, I can try to fix it. Looks like the pixels within this reference image have variable size; I expected all to be the same, but it's easy to adapt the margin on a per-pixel basis. |
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Margins are now calculated per individual pixel, which should get rid of the difference in the test image. |
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Ok, I think it's not so easy to get this perfectly right, as padding the pixels is already a bit hacky. As the heatmaps only look wrong if NaN is present, I now check for it and:
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| # Rectangles and polygons that are directly adjacent usually show | ||
| # white lines between them due to anti aliasing. To avoid this we | ||
| # increase their size slightly. | ||
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| if alpha(colors[i, j]) == 1 && margin_factor > 0 |
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What happens if using a transparent colormap here?
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The problem mostly goes away, but when you set alpha=0.99 for example, there are still some cases where artifacts occur. For example thin lines that shouldn't be there.
Description
Fixes #3619
CairoMakie heatmap cells are currently enlarged by a constant factor of 0.5. This PR changes this to a value relative to the pixel size.
Before:
After:
There are still some remaining inaccuracies, but its way better than before. This is really important for drawing halfway accurate maps.
Type of change
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Checklist