* Shapes: a hairline vector stroke no longer darkens the shape's edge pixels
A stroked shape with layer effects (or clipped layers) is drawn as our
fill plus a vector stroke fitted to Photoshop's own pixels: where those
pixels reach past our fill, the stroke takes the alpha the fill doesn't
explain, `(pixels - fill) / (1 - fill)`. It kept our stroke's colour for
that alpha. When Photoshop's fill covers more of an edge pixel than ours
(shapes snapped to whole pixels with Align Edges, our path a fraction off
the grid), the fitted alpha is mostly Photoshop's fill, so a 0.25 px grey
border on a white card was painted as a solid grey line: the edge came out
at the stroke's full colour (122) instead of Photoshop's 220.
The fitted stroke now takes the colour that, drawn Normal over our fill,
gives back Photoshop's pixel (un-compositing the premultiplied colour),
and keeps our colour only where the fitted alpha is negligible. Where
Photoshop's pixels agree with our fill this is our stroke's colour, as
before.
Test: hairline_vector_stroke_keeps_photoshops_edge_pixel_colour (edge
pixel 0.478 before, 0.86 after). The compose, gpu, io and engine tests
and the psd/io/engine corpus tests pass.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
* Shapes: neutral wording in the hairline-stroke fix; test it at 8, 16 and 32 bits
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---------
Co-authored-by: EthanSuquet <292885762+EthanSuquet@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: Brandon Thomas <echelon@gmail.com>
Co-authored-by: Tanish Manku <tmanku.dev@gmail.com>
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