Repair hot and dead photosites before the demosaic

A hot photosite went into the demosaic as it was read, and came out as a
coloured cross three pixels wide that nothing later could take back
out. Night and long exposures showed them; the defect-map reader added
for FR-RAW-3 was never wired in, and a CR2 carries no map anyway.

A pass over the mosaic now runs ahead of the demosaic, into a second
buffer. A photosite is hot when it reads more than twice every
same-colour photosite in its 5x5 window plus 2% of the range, and more
than twice each of its eight immediate neighbours of any colour. The
second half keeps stars and glints: real light reaches the sensor
through a lens and an anti-aliasing filter and lights a patch, so the
photosites beside it are lit too, where a hot photosite's are dark. It
is replaced by its brightest same-colour neighbour, which invents
nothing. Dead photosites are the mirror case, judged only where the
neighbourhood is above 5%, so shadow noise clipped at black is left
alone.

The colour of each photosite comes from a 6x6 sensor-anchored tile, so
Bayer and X-Trans share the pass. Export and every other path that
demosaics get it too, and there is no setting: the repair only fires
where a single photosite disagrees with everything around it.

Cost, warm, on a Canon 6D frame (RTX 3050): 91-99 ms to demosaic
before, 94-98 ms after; the extra pass is inside the run-to-run noise.

Tests render a frame with and without the defect and compare the
finished pixels. Without the repair a hot photosite showed by 230 and a
dead one by 168; with it neither shows, and a 3x3 highlight at white
survives.

This commit is contained in:

dtourolle

2026-09-27 06:20:23 -04:00

parent 6b99f67f47

commit c50d96e949

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docs/dev/traceability.md

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