The Automatic palette counts flat art's colours by area (a colour needs
about 1% of the picture, 0.5% at Colors 100) and fits that count with
median cut and area-weighted k-means. A stem, a highlight, or a near
white beside a pale background (within 24 levels, so in one box) was
averaged into a large neighbour; mixed-colour merging and Noise could
then remove what was left.
On the flat route only, after the count is fitted, rare_colours finds
the colours too rare or too close for it and keeps those that are
distinct (at least 2.5 in Oklab x 100 from every palette colour and from
the main colour each stands for), flat (mostly one histogram bin) and
drawn (a 4-connected region of their own unblended pixels of at least 8
pixels, or three of at least 4); a colour lying between two others, as
anti-aliasing mixes them, must also have an inside. At most six, largest
region first. They stay fixed while the other colours are refitted
around them; merge_mixed leaves them alone; denoise_keeping keeps their
regions of 4 pixels or more whatever Noise is (smaller specks still go).
Full Tone, Limited and Automatic's continuous-tone route are unchanged,
and denoise without kept labels is as before.
Methods cited in the code: median cut (Heckbert 1982), k-means (Lloyd
1982), Oklab (Ottosson 2020), salient-colour preservation (Fukuda et al.
2019, doi:10.1117/12.2521607). The rule and its numbers are VectorCraft's
own; Adobe does not document how its palettes are chosen.
Tests (code-drawn): a rare stem or patch over 2-8 flat colours, hard
and anti-aliased at 1x and 2x; near-white highlights on #FFF4E0 kept and
still paths at Noise 16; a 3 px #909090 stem on #808080; scattered
single pixels of the same areas add no colour; denoise_keeping at Noise
0-32.
Measured on 66 synthetic flat logos (22 designs x hard 1x, anti-aliased
1x and 2x; local inputs): every key colour and no spurious one in 66
(was 39); missing key colours 0 (was 43), spurious 0 (was 2), merged
pairs 0 (was 46); rendered dE00 0.348 -> 0.138. Four public-domain scan
crops take the continuous-tone route and are unchanged.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018tBcdwNhptqtmX32JCGFzB
The public documentation says Image Trace warns about images larger
than 1500 pixels on a side but traces them, only more slowly. VectorCraft
traced them silently, and refused any trace of more than 2,000,000
anchors, which a 4000 x 3000 photo at High Fidelity Photo nearly reaches
(1.9 million on a code-drawn photo) and a noisier one passes.
- imageTrace.make and makeAndExpand return `warnings`: one for an image
over 1500 px on a side (traced, but more slowly; a lower-fidelity
preset or a smaller copy is quicker), one for an image over 64 MP
that was traced from a scaled-down copy. The app shows the first in
the status bar.
- MAX_TRACE_ANCHORS is 8,000,000 natively (2,000,000 on wasm, where a
page has at most 4 GB). Measured through imageTrace.make on
code-drawn photos: about 90 bytes an anchor kept in the document;
7.9 million anchors kept 685 MB with an 876 MB peak (4000 x 3000,
Full Tone at Colors 100, Paths 100, Noise 1, 37 s).
- The refusal keeps its translated advice: raise Noise, lower Paths or
Colors, or pick a lower-fidelity preset.
Tests: a_large_image_traces_with_a_warning (1600 x 40 and 1500 x 8
code-drawn images, make and make-and-expand),
trace_warnings_name_a_large_or_scaled_down_image, a compile-time check
of the limit's range, and a UI test that the status bar shows the note.
Source:
https://helpx.adobe.com/illustrator/using/image-trace-results-optimization.html
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018tBcdwNhptqtmX32JCGFzB
