Merge pull request #7451 from dotCooCoo/fix/flat-logo-gray-between-black-and-white

Image Trace: Flat Logo traces a gray between black and white as one shape

docs/image-trace-adjustments.md

@@ -109,6 +109,24 @@ The trace then uses only the named colors, and white while white is a color of i
 color that was not named is traced too: each of its pixels goes to the named color, white or
 transparent that has the largest share in the blend of them that comes closest to the pixel.
 
+**Flat Logo with a color between two others.** When a traced color lies between two others, as a gray
+lies between black and white, an anti-aliased edge pixel between the outer two is also a blend of the
+middle color and one of them. Flat Logo then reads the pixel as the blend of the colors that lie nearest
+it in the flat areas within 6 pixels, when the pixel has a neighbor darker and a neighbor lighter than the
+middle color, along the line between the other two. A black disc beside a gray square on white traces
+with one gray shape, the square, and no gray slivers around the disc, when its edges are sharp or blurred
+by up to about half a pixel. An edge blurred by a pixel or more can still leave gray slivers along the
+disc, and so can an image with noise of a level or more in its pixels. A gray stroke two or three pixels
+wide beside black has no darker pixel next to it and stays gray. A soft-edged gray stroke about two
+pixels wide that touches black traces as black and white, and one about three pixels wide that touches
+black can lose most or all of its gray when it is short (12 pixels long or less). A line of gray one
+pixel wide between black and white stays gray when at least 13 of its pixels touch: such a line and a
+straight black-to-white edge whose pixels are as light as the gray give the same pixels, and both
+trace as gray. A one-pixel gray line between black and white that is shorter than 13 pixels, falls
+between pixels or is blurred traces as black and white. A flat area whose color lies between two named colors, as when the colors are named
+some levels off, counts as holding the named colors it is a blend of, and so do the pixels of exactly
+its color that touch it.
+
 **Large images.** An image of more than 1500 pixels on a side is traced as any other, only more
 slowly, and the trace says so: `imageTrace.make` returns the note in `warnings` and the status bar
 shows it (the [results optimization](https://helpx.adobe.com/illustrator/using/image-trace-results-optimization.html)
@@ -118,8 +136,9 @@ most 1024 pixels on a side: a larger decoded raster is averaged down in whole-nu
 image is traced at 513, and a 16,000 × 12,000 image, decoded at 9,459 × 7,094, is traced at 946 × 710), and the trace names both sizes in `warnings`. Flat Logo gives that note in place
 of the slower-trace note for an image over 1500 pixels and in place of the 64-megapixel note. An image at most
 1024 pixels on a side is traced at its own size, also when the named `logoColors` differ slightly from the
-image's colors. Only an image with more than 150,000 different pixel values that are not exactly one traced
-color is averaged down further: the factor doubles until at most 150,000 remain or the working copy has at
+image's colors. Only an image with more than 150,000 different pixel values to unmix (values that are
+not exactly one traced color, and values that are, at pixels outside a flat area) is averaged down
+further: the factor doubles until at most 150,000 remain or the working copy has at
 most 16,384 pixels (at most six times). A trace that would
 make more than 8,000,000 anchor points (2,000,000 on the web) is refused to protect memory, with advice:
 raise Noise, lower Paths or Colors, or pick a lower-fidelity preset. A trace keeps

docs/target-app-parity.md

@@ -1461,6 +1461,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
 - **Image Trace Flat Logo mode:** a fourth mode beside Black and White, Grayscale and Color, for flat-colour logos. Each pixel is read as a blend of the logo's colours (found automatically or named), the blend is interpolated smoothly and every outline is placed where two colours are equally present, so edges are accurate to a fraction of a pixel. Outlines are then cleaned: corners the blur rounded are put back, near-straight runs and near-circular arcs become exact lines and arcs, the rest is fitted with as few Béziers as the tolerance allows, touching colours overlap by a hair so no gap opens, and an outline that strays from the raw contour is fitted plainly instead. Gradients and photos are refused with advice to use Color. Line art whose only solid area is white paper (strokes a pixel or two wide) takes its colours from the strokes' cores, with the lighter shades along a stroke's anti-aliased edge folded into its ink; a page whose ink (a channel at least 48 below white) covers under 1% of it traces to nothing, as blank paper does. *Measured* (a local experiment, not run in CI): a flat-colour logo's vector original was rendered down to a soft 199 × 100 px transparent PNG, traced, and the result compared with the original at 1600 px wide. The built-in colour presets (6 Colors, 16 Colors, High Fidelity Photo, Low Fidelity Photo) had a mean edge error of 2.5 to 3.4 px and region overlap of 0.88 to 0.91; Flat Logo had 0.78 px and 0.966 (0.48 px and 0.975 from a crisp source), in about 0.1 s. Limits: flat-colour art only; needle-thin sharp tips are shortened by about 1.7 source pixels because the blur erases them; it works at no more than 1024 px on the long side (larger images are averaged down first); only one logo family has been scored against a vector original.
 - **Image Trace, Flat Logo named colors only:** with `logoColors` named, `"logoWhite": false` traces those colors only, so white areas take the nearest of them and no white is added; a named white is kept, and enclosed transparent areas stay holes; code-drawn tests in `crates/trace` and `crates/engine`.
 - **Image Trace, Flat Logo flat-art check with named colors:** with `logoColors` named, whether the image is flat art is judged by its own colors, as many as are named, with white, or as the Colors setting gives, whichever is more. Named colors 20 levels off a flat badge's colors still trace it, a hatch on a light ground gives the same result with close and far named colors, a gradient's refusal score does not depend on how far the named colors are from it, and areas of colors that were not named are traced in the named colors instead of being refused; code-drawn tests in `crates/trace`.
+- **Image Trace, Flat Logo with a color between two others:** an anti-aliased edge pixel between black and white is read as a blend of black and white, not of black and a gray that lies between them, when the flat areas around it and the pixels beside it show that edge, so a black disc beside a gray square on white, with sharp edges or edges blurred by up to about half a pixel, traces with one gray path, the square, instead of the square plus 8 to 24 gray slivers around the disc with the colors found or named exactly (an edge blurred by a pixel or more, or pixel noise of a level or more, can still leave gray slivers); gray strokes two and three pixels wide beside black stay gray (a soft-edged gray stroke about two pixels wide that touches black traces as black and white, and a short one about three pixels wide can lose most or all of its gray), and a one-pixel gray line of at least 13 touching pixels between black and white stays gray (a shorter one, or one that falls between pixels or is blurred, traces as black and white); code-drawn tests in `crates/trace`.
 - **Image Trace, Keep Colors:** `"keepColors": ["#rrggbb", …]` traces only the palette colors near a listed color (Abutting: each with the paths the trace of every color gives it; Overlapping: not reaching under the colors left out), in Black and White, Grayscale and Color; code-drawn tests in `crates/trace` and `crates/engine`.
 - **Advanced art:** live Blends (steps/distance/smooth colour, editable spine, anchor-targeted Blend tool, faithful interpolation, knockout), Envelope Distort (warp/mesh/top object, Reset, full Envelope Options, mesh handles, Edit Contents; type, images, symbols, gradients, patterns and appearance distorted everywhere), Liquify tools with options and pen pressure, Puppet Warp with rotating pins, Perspective Grid with presets, movable planes and projected type (choosing a perspective tool shows the grid; Hide Grid hides it with the tool still chosen), Gradient Mesh, Shape Builder (stroke-only open paths and lines cut the regions they cross and enclose regions of their own, and regions they bound merge without seams where the lines cross at rounded coordinates (#893); filled open paths count as closed; erase mode while Alt/Option is held: a minus pointer, red highlights of what will go, a click or drag deletes the regions touched, the pieces of open lines and the edges (outline pieces between the points where paths meet, opening their paths there) it passes over, one undo step, `shapeBuilder.merge {erase}` and `shapeBuilder.regions` edges over MCP), Live Paint (every path an edge, open lines included), Image Trace (12 presets, colour layers traced in parallel; a trace past two million anchor points is refused with advice rather than running out of memory, an image over 64 megapixels is traced scaled down to that size (aspect kept, paths at the image's own size) and one over 192 megapixels is refused, and a selection too large to outline shows its bounds (#525); Object › Image Trace › Make and Make and Expand trace at once with the Default preset, #543; with an image selected the Control bar and the Properties panel show Image Trace, whose arrow traces with any preset, Mask (`object.maskImage`: a clipping path on the image's outline, selected so its handles crop), Crop Image (a crop box on the image, starting on its part over the artboard, dragged by its handles or inside it, the outside dimmed, with X/Y/W/H, Apply and Cancel in the Control bar, Enter and Escape, #734; an image that isn't turned or skewed, isn't CMYK and can be read at its recorded size is cut from its own pixels when the crop edges fall on its pixel grid, copied as they are without resampling; any other image is drawn, #5534; `object.cropImage {rect}` for agents, `{trim: true}` cuts an image to its pixels that aren't fully transparent, pixel for pixel) and Embed or Unembed in place of Fill and Stroke; with an Image Trace object selected, its Preset (choosing another traces again), View, the Image Trace panel and Expand, plus Release in Properties; the five View modes (Tracing Result, with Outlines, Outlines, Outlines with Source Image, Source Image) redraw a trace on screen without tracing again, are saved with it and `imageTrace.setView` sets them, while exports and Expand keep the result; the panel's Advanced section is a header that stays open or closed as it was left (part of #641); Color mode's Palette: Limited, Full Tone (as many colours as the tones need, Less … More), Automatic (flat art with its own colours, else Full Tone; a heuristic) and Document Library (the most used colours of the document's swatches or a swatch library, filled with the swatch colours as they are), part of #641; Advanced › Create: Fills and/or Strokes, where lines up to the Stroke width trace as stroked centre lines (distance transform, thinning, a skeleton graph with spurs pruned, curve fitting; one width per line; without Fills, wider areas become stroked outlines), part of #641), pattern swatches with pattern editing mode, live Repeat (radial/grid/mirror). A single selected mirror repeat shows a prominent axis with a center move handle and two rotation handles. Drag the line or center to change spacing, or an end to change angle; Shift snaps rotation to 45°. The original artwork stays in place, the reflected copy previews live, Escape cancels and each drag takes one undo step through `object.repeat.options`. Controls follow zoom/view rotation and hide with edges or the bounding box. Engine and headless canvas regressions passed for gestures, history and visibility; native move, rotation and Escape screenshots were reviewed. [Public mirror-repeat reference](https://helpx.adobe.com/illustrator/desktop/paint-and-fill/create-and-edit-patterns/set-mirror-repeat-options.html). A single selected grid repeat shows a handle below the grid for rows, one right of it for columns and one past its bottom-right corner for both, and sliders between its first two columns and rows for the horizontal and vertical spacing; the source keeps its size, each drag is one undo step and Escape cancels it ([public grid-repeat reference](https://helpx.adobe.com/illustrator/desktop/paint-and-fill/create-and-edit-patterns/set-grid-repeat-options.html), #2691). Object › Expand turns radial, grid and mirror repeats into groups of their instances (#1765, #1756).
   Choosing the Blend tool again while it is active (its toolbar button, W or `tool.select`) finishes the blend: the object clicked first is dropped and the next click no longer adds to the blend just made, so the click after it starts a new blend ([Blending objects](https://web.archive.org/web/20241217212108/https://helpx.adobe.com/illustrator/using/blending-objects.html)).