The check for colors the palette cannot explain counted a pixel of a
bar two pixels wide only when its neighbors on both sides along the
bar were bar pixels. In a bar three pixels long only the two pixels of
its middle row passed, so its color had fewer than the three pixels a
color needs and was not added to the palette. A pixel now counts when
it lies at either end or in the middle of three such pixels in a row,
so all six pixels of a 2 × 3 bar count.
Flat Logo counted the anchors of every fitted outline and hole before it
left out the ones with no area, so a trace whose kept paths fit the
anchor limit could still be refused as too complex. The limit now counts
the anchors of the subpaths that go into the result.
The limit on outlines per color also counted holes, which are cut only
with Ignore White on. Holes now count toward it only when they are cut.
When Flat Logo finds the colors itself (no colors named), a flat bar
two pixels wide (whole pixels of one color) on a ground beside other
art was lost or traced in another color. No bar pixel has a uniform
3 x 3 neighborhood, so neither the first clustering nor the check for
unexplained colors took it. A gray bar on white beside black art was
traced as white, and a red or green bar was traced as black. Bars
three pixels wide or more were already found.
The check for unexplained colors now also takes the pixels of such a
bar: two rows or columns of one color (within about 3.5 in RGB
distance), three pixels long, with the same ground on both sides. They
count when the known colors do not explain them, and also when their
color lies less than two thirds as far from the ground's known color
as from every other known color, where the bar would otherwise be
traced as the ground. A gray bar darker than about #9B9B9B on white
beside black art stays black, #808080 included, because a black stroke
1 to 1.6 px wide on the pixel grid gives the same pixels. Named colors
are unchanged.
The fit of a thin outline can lose all its area. Its two sides can
straighten onto one line, which leaves two anchors whose segments run
back and forth along it. Or the fit can be a single cubic, which becomes
one anchor and has no segment. Both occur when Flat Logo traces noise
whose cells are one pixel in size. The trace kept such an outline as a
selectable path that paints nothing.
Flat Logo now leaves out an outline whose area is below 1e-6 px^2,
together with its holes, and a hole whose area is below 1e-6 px^2. The
area is summed about the outline's first anchor, as the other trace
modes already do for a filled loop (crates/trace/src/lib.rs:996-1001).
Outlines with an area of 1e-6 px^2 or more, thin slivers included, are
kept as before.
One test traces a black and cream noise with both colors named exactly
and checks that no subpath of the result lacks an area. Two more build
shapes from straight cubics: a hole without area is left out, and an
outline without area is left out with its hole.
Flat Logo traces a copy of the image at most 1024 pixels on a side,
averaged down by a whole factor, so a 1025-pixel image is traced at
513 pixels. The trace's warnings did not say so, because they compared
the image only with the decoded raster. For an image over 1500 pixels
they said instead that it is traced more slowly, which Flat Logo does
not do.
The trace result now carries Flat Logo's working size when it averaged
the image down. imageTrace.make and imageTrace.makeAndExpand then name
both sizes in their warnings, and the status bar shows that note, in
place of the slower-trace and megapixel notes. Other modes keep their
warnings. The message has a row in each catalog that translates the
other Image Trace warnings.
Found while testing crates/trace/src/logo/palette.rs:9-15 (parse_hex)
Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Raster::new checked its RGBA length with assert_eq!, so bytes of the
wrong length (from a file, a plug-in or a control message) would abort
instead of reporting an error. It now returns Result<Raster, TraceError>
and gives TraceError::Decode naming the byte count and the size (the
existing variant, whose text is already translated, instead of a new
message every language would need). The size product is checked for
overflow.
Raster::pixel indexed the bytes directly; it now gives transparent
black outside the raster, or past the end of a raster whose public
fields were set to a size its bytes don't have (which mosaic reads).
The public signature changes: every caller in the workspace was a test
(trace unit tests, Flat Logo tests and the quality harness), updated to
unwrap. No shipped code built a Raster with new; decode, decode_to_fit
and from_fn always make the right length, and trace_within already
refuses a raster whose fields disagree.
Test (code-drawn): a_raster_of_the_wrong_length_is_an_error_not_a_crash
(short, long, empty, zero-width and overflowing sizes; pixel, trace and
mosaic on a raster whose fields disagree).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018tBcdwNhptqtmX32JCGFzB
A small closed loop whose fit collapsed to a single cubic (fit_closed),
or a piece returning to its own junction with fewer than two fitted
cubics (fit_piece), kept every positioned point as a straight segment.
A looser Paths collapses more loops, so it could give more segments
than a tighter one.
Such a loop now tries the fewest segments that still hold it, each only
if the result keeps an area (more than 0.25 px^2) and stays within
1.5 * max(tolerance, 0.5 px) of the points both ways: the fit at up to
three somewhat tighter tolerances (what a slightly higher Paths gives);
for a closed loop then two cubics split at its start and its farthest
point, then the outline simplified at the tolerance and finer. The
positioned points stay the last resort, as before.
Test (code-drawn): a_higher_paths_never_gives_fewer_segments sweeps
Paths 0/25/50/75/100 over 32 seeded 48 px images of soft blobs plus
pixel noise in Color and Black and White at Noise 1 and 3. Before, six
runs had fewer segments at a higher Paths (e.g. 125 -> 79 from Paths 0
to 25); after, none. One image (seed 16, Black and White: 140 -> 136
from Paths 0 to 25, with or without this change) has another cause and
is left out of the sweep.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018tBcdwNhptqtmX32JCGFzB
Flat Logo found its colours only from solid pixels (a uniform 3 x 3
neighbourhood). Line art on paper has no solid area but the paper's: a
stroke one or two pixels wide never fills one, so its colour was a handful
of pixels among tens of thousands of white and was cut as noise (under
0.1% of the solid pixels). The palette came back empty and trace_logo
returned an empty TraceResult, which imageTrace.make reported as a success
with paths 0, anchors 0, colors 0.
Cause: logo::palette::auto_palette had no way to find a colour that has no
solid area, and logo::pipeline::trace_logo treats an empty palette as
nothing to trace.
Fix: when the solid pixels give no colour but white, auto_palette reads
the colours from the strokes' cores instead (line_art_palette): the opaque
ink pixels at least as far from white as each of their four neighbours,
the middle of each stroke where it is least blended with the paper.
Two guards keep that fallback to line art:
- Ink is a colour at least 48 below white in one channel, and the page
must have ink on at least 1% of its opaque pixels. Light grain and a few
sparse marks on otherwise blank paper stay blank, as plain white does.
- The lighter shades along a stroke's anti-aliased edge are local maxima
of their own; a colour that lies on the line from white to a darker
colour of the palette (within 20) is a blend of that ink with the paper
and is folded into it (fold_fringes), the ink keeping its colour.
The rest of the pipeline (unmixing, the flat-colour check and its NotFlat
refusal) is unchanged, and images with a solid colour other than white
never reach the fallback.
Tests (code-drawn inputs):
- thin_line_art_on_paper_is_traced_not_blank: four 2.4 px dark strokes
and two red marks on white. Before: palette [], no paths. After: dark
and red paths along the middle of every stroke and mark.
- anti_aliased_coloured_lettering_has_only_its_inks: rings, slants and
bars 1.6 px wide in red, blue and green. Without the fold: six colours
besides white; after: exactly the three inks.
- sparse_marks_on_paper_are_not_promoted_to_colours: 24 grey 12 x 2 px
marks of 239, 223 or 191 on a 256 x 256 page (under 1% ink). Without
the guard: palette [white, #efefef]; after: empty palette, no paths.
- grainy_blank_paper_has_no_ink: paper grain 243-255 traces to nothing.
- edge_shades_fold_into_their_ink_and_other_colours_stay (unit).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018tBcdwNhptqtmX32JCGFzB
Create: Strokes drew every line with round caps: a square-ended line 10 px wide
had its corners 2.94 px outside the stroke.
- A line's ends are square when its ink reaches as far a third of the width to
either side of its middle as along it (a round end stops short there by a
seventh of the width); told from lines 3 px wide and more, all the ends of a
line together. The stroke then has square caps (`TracedPath::square_caps`).
- The last points of a wide line's skeleton can turn towards a corner of its
end. An end that has left the line the skeleton followed a width back (by a
quarter of the width, 1 px at least) is put back on it; and an end may be
pulled back as well as pushed out to where the ink ends.
Outline on the thin-line inputs: largest distance from the art 2.94 -> 0.88 px
(clean 2.94 -> 0.41; aliased 0.88 -> 0.81), mean 0.055 -> 0.050 px, anchors
14 -> 10.
A scan's paper is a tenth darker in one corner than in another. Flat Logo found
each tone of it as a colour of its own and traced the bands and the specks
between them: on the scanned inputs 470 paths, 21 px from the art on average.
Two palette colours are now one when the pixels between them are no fewer than
a third of those at the lesser of the two: flat colours leave only their shared
edge between them, tones of one colour fill the gap. Whether the image is flat
art at all is still asked of the tones as found.
Flat Logo on its inputs, all sizes and variants: 3.106 -> 0.090 px off on
average, 88.5 -> 0.82 px at most, 69.9 -> 3.9 paths; clean, aliased, blurred
and noisy art as before.
Gradients (params `gradients`, a checkbox in the panel for Grayscale and Color;
off unless asked for): an area whose colour changes evenly along one direction
is traced as one path filled with a linear gradient, not as bands of flat colour.
Gradients are found before the palette is made, so no colour is spent on their
bands: a connected run of smoothly changing pixels is a gradient when a plane
fits each colour channel with all three sloping the same way, the colours along
that way are at most six stops with ramps between them, and painting them back
gives the area's own pixels. Flat colour, soft edges between flat colours and
shading that goes two ways are left as they were.
The harness gains two linear-gradient inputs with known lines and stops, and
measures whether each is found, the angle of its line and the colours of its ramp.
Shapes (params `shapes`, a checkbox in the panel; off unless asked for): a filled
outline that is a circle, an ellipse, a rectangle or a regular polygon comes out
as that live shape. A shape is only made when every point of the traced outline
lies within 0.5 px (0.2% of the shape's size, if more) of it; an ellipse whose
radii differ by less than twice that is a circle of its area.
The outline before fitting: a corner's own pixel no longer pulls the two edges
that meet there, and a one-pixel step between two long edges is the corner where
they meet. Sharp corners kept: Default 69% -> 76%, the colour presets 86% -> 91%.
The harness gains plain-shape inputs and "shapes %".
The documented option "replaces slightly curved lines with straight lines and snaps lines near 0 or 90 degrees
to absolute 0 or 90 degrees" (helpx, Image Trace panel options); ours did the first half only.
- With Snap Curves To Lines, a straight piece at least 2 px long and within 2.5 degrees of level or upright is
made exactly so, by moving its ends across it to their mean (the page gives no angle: 2.5 degrees is our
choice). The pieces next to a moved end follow it.
- A junction other regions share stays where it is, so abutting regions still have one curve along their edge;
a line between a junction and a free end is levelled to the junction.
- The harness gains askew inputs (a rectangle, a plus sign and two lines, 1 to 2 degrees off level and upright)
and an "upright %" column: the share of the outline length that is exactly level or upright.
On the clean askew inputs (docs/image-trace-quality.md): Black and White Logo and Technical Drawing, the presets
with the option on, go from 0% to 91% and 95% of their outline exactly level or upright. Their outlines are then
0.49 and 0.59 px from the art as drawn where they were 0.05 (4.2 px at the far end of a 300 px side turned 1.5
degrees): that distance is what the option is for. Presets without the option are unchanged.
Against the documented panel (https://helpx.adobe.com/illustrator/desktop/manage-objects/traces-mockups-symbols/image-trace-panel-options.html):
- Ignore Color: "Ignores a specific color while tracing. Use the color picker to selectively ignore a color."
The panel's Ignore White is now Ignore Color with a colour button beside it (white until another colour is
picked); `imageTrace.make` takes `ignoreColor: "#rrggbb"` beside `ignoreWhite`, and leaves out the palette
colours within about 30 levels of it. Documents saved before have no such setting and ignore white as they
did. Flat Logo mode leaves out white only.
- Auto Color ("Creates a posterized image from a photo or artwork"): Color mode with the Automatic palette.
- Outline ("Simplifies the image to black outlines"): Black and White with Create: Strokes and no fills.
- The Outline preset's name is translated as a preset's name, not as the Outline view's.
Measured (docs/image-trace-quality.md): Auto Color on flat art is 0.140 px off on average with 4.0 paths (16
Colors: 0.141, 4.2). Outline on the line inputs, the first measure of Create: Strokes: 0.310 px off on average,
1.84 at worst, 81 anchors for 5 lines (Line Art's filled outlines: 0.055, 0.96, 46).
Each region's outline was fitted on its own, so the edge between two regions was fitted twice, a little
differently, and left hairline gaps and overlaps.
- An outline is cut at its junctions: the pixel corners where three or more regions meet, where two parts of a
region touch by a corner only, and where an edge reaches the image's border (each side of the image is a
neighbour of its own, so the image's corners stay exact). A junction lies where the edges around it say, the
same for every region around it.
- Each piece between two junctions is the whole edge between two regions. Both get exactly the same points for
it (shifts are rounded to 1/1024 px so that the two sides agree to the last bit; whether a piece is hard is
decided by the piece alone) and it is fitted the same way from either side (from its end further left), so it
is one and the same curve in both paths. A loop without junctions is fitted clockwise from its leftmost point:
a shape's outline and the hole it leaves in the shape around it are one curve too.
- Stacked layers (Overlapping) share no edges and are cut at the image's border only.
On each preset's own inputs, all sizes and variants (docs/image-trace-quality.md), before -> after:
- Default: gaps 22.2 -> 0.8 px, overlaps 22.4 -> 0.5 px
- 3 Colors: gaps 48.6 -> 0.0, overlaps 29.4 -> 0.0; outlines 0.087 -> 0.104 px off on average
- 6 Colors: gaps 39.0 -> 0.2, overlaps 35.7 -> 0.3; 0.137 -> 0.140 px off, largest 1.09 -> 1.34
- 16 Colors: gaps 34.5 -> 0.2, overlaps 26.4 -> 0.2; 0.133 -> 0.141 px off, largest 1.09 -> 1.31
Each crack between an inside and an outside pixel is moved to where the pixels across it say the edge is (the
blend of the two tones in the column of pixels across the crack; a thin line by the centroid and sum of its
tone; hard-edged images are read as staircases), and the outline is fitted as Flat Logo mode fits its own:
corners put back, straight runs as lines, a round outline as a circle, the rest as few curves as Paths allows.
Snap Curves To Lines straightens slightly curved runs and makes arcs. A fit that strays from its outline
gives way to a plainer one, and at last to the outline's own points.
On each preset's own inputs, all sizes and variants (docs/image-trace-quality.md):
- Default: outlines 0.313 -> 0.091 px off on average, largest 1.51 -> 1.02; edge error 17.2 -> 10.1;
gaps between abutting paths 63.5 -> 22.2 px, overlaps 67.0 -> 22.4 px
- Black and White Logo: 0.270 -> 0.064 px off, kinks 15.3 -> 0.3, anchors 3.78 -> 2.73 times the art's
- Technical Drawing: 0.201 -> 0.086 px off; Line Art: 0.158 -> 0.093
- Worse: anchors on blurred and scanned thin lines (Line Art 25 -> 77 on average), High Fidelity Photo
(colour error 2.30 -> 2.50, anchors 46,866 -> 81,597, 1 megapixel photo-like image 0.37 -> 1.98 s)
A fourth Image Trace mode for flat-colour logos. The existing tracer follows hard pixel
edges, so an outline can only be as good as the pixel grid; here each pixel is read as a
blend of the logo's flat colours, the blend is interpolated smoothly (cubic B-spline), and
every outline is placed where two colours are equally present, to a fraction of a pixel.
Outlines are then cleaned the way a person would:
- corners the blur rounded are put back (line fits either side of a bend, intersected);
- near-straight runs and near-circular arcs become exact lines and arcs (Snap Curves To Lines);
- the rest is fitted with as few cubic Beziers as the tolerance allows (Schneider);
- touching colours overlap by 0.06 px so no hairline gap opens between independent fits;
- shapes are painted biggest first; transparent areas fully enclosed by artwork (letters
knocked out of a badge, the counters of an "o") are painted white so the logo reads the
same on any background, or become real holes with Ignore White (each hole belongs to the
smallest outline containing it);
- an outline whose fit strays more than 1.4 px from the raw contour is fitted plainly.
Colours are found automatically (and completed from pixels no blend of the known colours
explains, so a small accent is not lost) or named with `logoColors: ["#rrggbb", ...]` (white is
always its own class; colours closer than 12 count as one; at most ten). Gradients and photos
are refused with advice to use Color (a flat-colour score of the solid areas, 0.93). A
hard-edged source with no anti-aliasing is softened by under a pixel and fitted with looser
snap tolerances. Images over 1024 px on the long side are averaged down first (further, if
they are busy enough to make the unmixing expensive) and the result is mapped back exactly.
More real outlines than we will fit are refused, not silently truncated.
Also: a "Flat Logo" preset, the mode in the Image Trace panel (Method hidden: it always
stacks), the command docs and MCP prompt, es/fr/it/ru translations for the two new messages
and the mode name, and the ROADMAP.
Never-crash: no unwrap/expect/panic, every size and float is bounded and checked, with
tests for degenerate and extreme input (NaN/infinite parameters, 0x0 and 1x1 images, sparse
outlines, an anchor budget, a 200,000-entry palette) and a 250-run randomised no-panic
property test. The B-spline interpolation follows Unser et al. and Thevenaz et al., and the
curve fitter follows Schneider (Graphics Gems); both are written from the papers.
Measured (local experiment, not in CI): a flat-colour logo's vector original rendered down
to a soft 199x100 px PNG and traced. Mean edge error vs the original at 1600 px wide:
built-in colour presets 2.5 to 3.4 px, Flat Logo 0.78 px (0.48 px from a crisp source);
region overlap 0.88-0.91 vs 0.966. About 0.1 s for a 200 px logo.
Tests: 60 new in the trace crate (unmix, field, contours, geometry, Beziers, corners,
outline fitting, palette, end-to-end on synthetic shapes made in code) and 3 in the engine.
cargo xtask ci passes (fmt, clippy, test, assets, brands, layers, wasm): 4,290 tests.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
aiongg