Grzegorz MartensandClaude Opus 5.5 c412093dc7 M11: an indexed image's palette says which of its samples is dark, so it is averaged too ...

#5426 left indexed images at their resolution rather than guess which sample is
dark. The palette says: dark_is_one now maps samples 0 and 1 through the decode array
to palette entries (rounded and clipped to hival, ISO 32000-2 §8.9.5.2) and compares
how light those entries are (`lightness`: the grey, or Rec. 601 luma over DeviceRGB).
Only DeviceGray and DeviceRGB bases count, the table a string or a stream (within
4 KiB), directly or by reference: there the palette's values are the colour, and
under /DefaultGray or /DefaultRGB no polarity is asked for. Other bases (CMYK,
calibrated, ICC-based, a resource name), two entries alike, an entry the table
doesn't hold or a hival past 255 still say nothing; separations and DeviceN still
aren't averaged, their tint transforms unread. #5426's tone guard applies as to any
image.

#5426's indexed thin-rule test now checks what it was for: with the palette either
way round and the decode array either way, the averaged image holds the averaged
DeviceGray one's samples (flipped where its samples are) and renders the same. A unit
test covers each base, both orders, an inverting decode array, the weights of luma,
the table by reference and in a stream, and every refusal; the older polarity test's
doc says what is known now.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

2026-10-30 19:04:42 +01:00

..

jpeg_color_transform.rs

style: rustfmt the cancellation test

2026-10-23 10:53:16 +02:00

optimize.rs

M11: an indexed image's palette says which of its samples is dark, so it is averaged too

2026-10-30 19:04:42 +01:00