GeneratePixmap wrote every pixel twice: once into the QImage and once into
image_rgb. The only reader was writePixelLabels, which needs a colour for at
most 5000 pixels and only above 30x zoom, so the mirror cost a W*H*3 buffer
and a second store per pixel to serve a fraction of a percent of them.
Read the colour back from the rendered image instead. 18.1 Mpx colouring loop:
9.5 -> 6.2 ms.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
leonarski_fandClaude Opus 5
0cee55f654