Illustrator 30.0's gradient Method, from the public documentation
(https://helpx.adobe.com/illustrator/desktop/paint-and-fill/create-and-edit-gradients/control-perceptual-interpolation-in-gradients.html):
Classic or Perceptual; perceptual interpolation matches colour transitions to
how the eye perceives differences between colours, and perceptual gradients
are rasterised when saved as PDF or SVG.
- Gradient gains `method` (Classic | Perceptual; serde default Classic,
written only when Perceptual, so older files open as Classic and Classic
files are written as before). The colour crate's OKLab helpers open up for it.
- Perceptual mixes neighbouring stop colours in OKLab (sample, and
sample_keep_model for the stroke meshes, Expand and blends); opacity stays
linear. Renderers that mix linearly get stops on the perceptual curve,
placed by halving each half segment where a straight line strays more than
0.4 of a colour level (a nearly straight segment needs none). Classic
gradients expand exactly as before.
- draws_as_pixels includes Perceptual gradients, so SVG and PDF write a
Perceptual fill or stroke as an image at the document's raster effects
resolution, clipped to what it paints. A gradient along or across a stroke
stays slices (PDF no longer draws it as a within-stroke image).
- With Dither: a dithered Perceptual fill is the perceptual mix with dither's
noise (the canvas's dithered grids are keyed by method too); SVG and PDF
write it as an image with the noise, and a dithered Perceptual stroke as an
image without it, as the canvas draws it (GradientPaint::pixels, SVG's
raster_paint and PDF's area are told whether they paint a fill).
Review follow-up (CodeRabbit): a dithered fill skipped set_paint's guard for
a gradient without stops and sampled a transparent grid to draw nothing. It
now takes the same no-fill path.
Review follow-up (CodeRabbit): a large dithered gradient mostly off-screen
sampled its whole grid (up to 4096 x 4096 cells, 64 MiB) to draw a small
visible part, and did it again on each zoom step. The renderer now samples
only the cells the render target can show, a cell more each way for the
bilinear mix, snapped out to 256-cell tiles so a pan within them reuses the
grid. Cells keep their place in the whole grid, so the gradient and its
noise are the same pixels as before (GradientPaint::pixels_within).
Illustrator 30.0's gradient Dither, from the public documentation
(https://helpx.adobe.com/illustrator/desktop/paint-and-fill/create-and-edit-gradients/control-dither-in-gradients.html):
a Dither checkbox in the Gradient panel; dither converts the gradient into
pixels with subtle noise, works with gradient fills only, and follows the
Document Raster Effects resolution.
- Gradient gains `dither` (serde default false, written only when on, so
older files open unchanged and new files keep it).
- The renderer draws a dithered linear or radial fill as an image paint: the
gradient sampled a cell per device pixel or finer (quarter-octave steps,
cached per thread), each channel given seeded triangular noise of up to a
level before rounding. Same pixels every run; strokes and undithered fills
draw exactly as before. PNG and other raster exports go through it.
- SVG and PDF write a dithered fill as an image at the document's raster
effects resolution, clipped to the shape (the freeform-gradient path);
characters' fills stay vector gradients in SVG, with a warning.
- paint.editGradient and paint.setFill take `dither`; strokes refuse it.
The Gradient panel's Dither box is dimmed behind the Stroke proxy.
- i18n rows in all 24 catalogs; docs: G13, target-app-parity, ui-parity,
mcp.md, plugins.md.
Taha-Mahmoodi