Indexed export (GIF, PNG-8, BMP, TIFF) finds each pixel's nearest
palette entry with a linear scan, and the k-means refinement in median
cut does the same once per cell per pass. With the 256-entry palettes
this code produces, that is 256 distance evaluations per query.
PaletteIndex is an exact nearest-neighbour kd-tree over the palette,
balanced at the widest weighted axis, with tight channel bounds in every
subtree so branch-and-bound can skip whole boxes. Small palettes (12 or
fewer entries) keep the scan, which is cheaper than tree traversal.
Results match the linear scan exactly, including ties: an equal-distance
entry with a smaller index still wins. The bound uses the same weighted
squared f32 form as dist() rather than a transformed space, so rounding
cannot change which entry is chosen.
Three tests: randomized parity against the original scan across palette
sizes spanning the cutoff, three weight vectors, duplicate colours and
fractional query points; explicit tie-breaking cases; and an opt-in
benchmark comparing 100k queries at both, behind -- --ignored.
File > Export > Save for Web (Legacy) (Ctrl/Cmd+Alt+Shift+S) opens a dialog with Original,
Optimized, 2-Up and 4-Up views showing each file's size and download time, and settings for
colour reduction, colours, dither, transparency and matte, interlacing, web snap, lossy GIF,
JPEG quality, the colour table (lock, map to transparent, web shift, sort), image size and
anti-aliasing, Clip to Artboard, sRGB, metadata, slices (all or selected), HTML output and
presets. Preview in Browser opens the HTML page.
Engine: document.exportForWeb, document.exportForWeb.preview (its byte count is the size of
the file Save writes), webExport.settings and webExport.presets.list/save/delete. Saved presets
and the remembered settings are stored in Prefs. Render: quantize_locked, and encode::web for
web snap, colour table edits, lossy GIF and GIF/JPEG comments. PNG files get an sRGB chunk.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
document.export {format: "bmp"} writes BMP through the raster export path:
depth 1 (black and white), 4 or 8 (a palette by reduction and dither,
optionally RLE4/RLE8), 16 (5-5-5), 24 or 32 (with alpha, a version 4
header); colorModel rgb or gray; fileFormat windows or os2 (a core header);
flipRows writes top-down rows (a negative height). Impossible combinations
are refused as bad params. Export As offers it with the bmpOptions dialog,
which keeps its choices writable together; BMP moves from read-only to read
and write (tests that used .bmp as the unwritable format now use .dwg).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
document.export {format: "png8" | "gif"} reduces the art to a palette of at most `colors`
(2–256) entries: median cut over a 15-bit histogram refined by k-means (perceptual,
selective or adaptive weighting), or the web-safe, black-and-white or grey palettes; art
with that many colours or fewer keeps them exactly. Dithering is Floyd–Steinberg diffusion,
an 8×8 ordered pattern or noise, with an amount. Pixels under half opacity become one
transparent entry; partly transparent edges blend over the matte. PNG-8 is an indexed PNG
(PLTE, tRNS, 1–8 bits per pixel, Adam7); GIF is a GIF89a (optionally interlaced). Both are in
document.formats, Export As (PNG-8 / GIF Options dialogs) and Export for Screens.
document.formats' writable list and the MCP export tool's format enum gain gif and png8
(their tests list them).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
bflatastic
Ayanprogrammer11