i12bp8 99bcc162b8 web-image-prep: chroma-contracted quantiser for newsprint illusion ...

Previous version pulled accent ink too aggressively (accentPull 0.85)
so anything red-leaning collapsed to solid red. Real photographic feel
from a 3-ink palette comes from W/B halftones simulating greys with
the chromatic ink only sparsely overlaid - the newsprint illusion.

Three knobs now make this work:
  - L_WEIGHT 3.5 (was 1.6): lightness completely dominates the metric
  - CHROMA_CAP: source a/b axes pre-scaled to the achievable accent
    chroma so the dither isn't asked for more colour than one ink can
    deliver. Excess chroma gets dropped via FS error diffusion through
    B+W neighbours.
  - accentPull 0.06 (was 0.85): only a tiebreaker bonus, used in the
    most strongly hue-aligned pixels.

2026-04-26 21:03:10 +02:00

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web-image-prep: chroma-contracted quantiser for newsprint illusion

2026-04-26 21:03:10 +02:00