DM-55580: Make mask display faster - #23
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timj
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Jul 22, 2026
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- There was a imshow call that was not needed because it was immediately followed by imshow.
- We were calling imshow per mask plane and that was not only causing rendering each time but also additional matplotlib overhead. This patch creates a high res composite mask image first and then hands it off to matplotlib once.
erykoff
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Are you sure that the draw_idle isn't needed?
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This redraw is not needed because the calling code immediately redraws.
Displaying an Exposure previously drew the mask with one imshow per set bitplane, so a coadd with many populated planes produced a dozen full-resolution overlay layers. Every repaint then colour-mapped and resampled each layer independently, which dominated the display time (the resampling itself is cheap; generating the full-resolution RGBA for each layer is the cost). Blend the visible planes into a single full-resolution RGBA image and draw it as one layer instead. The Porter-Duff "over" operator is associative, so this is equivalent to drawing each plane separately but leaves matplotlib with one layer to colour-map and resample rather than one per plane; rendered output matches the old path to within 8-bit rounding. fastMaskDisplay is unchanged. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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