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Revert "remove plus clamp"

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This reverts commit 539909a84a.

Reason for revert: Brian and I think ultimately clamping is saner.

Original change's description:
> remove plus clamp
> 
> Clamping for plus mode should happen only as the destination format
> requires it, or as a consequence of the limited range we're holding
> colors in the pipeline, or because non-normalized alpha is nuts.
> 
> So I've taken away the clamp on float rgb, keeping it on lowp to stay
> in its legal range, and on float alpha because it's crazy not to.
> 
> Open questions:
>   - also clamp alpha to zero?
>   - what do we do with alpha <0 or >1 in general, beyond plus?
> 
> Cq-Include-Trybots: luci.chromium.try:linux-blink-rel
> Change-Id: I15660ce55cc393e312f18ffdc13bbfdef08ac6e0
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/201040
> Reviewed-by: Brian Osman <brianosman@google.com>
> Commit-Queue: Mike Klein <mtklein@google.com>

TBR=mtklein@google.com,brianosman@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: Iccf3fd9d2b6bf541b0e2fed4f98bf41124deeedf
Cq-Include-Trybots: luci.chromium.try:linux-blink-rel
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/201530
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
This commit is contained in:
Mike Klein 2019-03-15 14:03:41 +00:00 committed by Skia Commit-Bot
parent b9008539c5
commit b90c0807e4
1 changed files with 2 additions and 16 deletions
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18
src/opts/SkRasterPipeline_opts.h
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@ -1124,6 +1124,7 @@ BLEND_MODE(dstover) { return mad(s, inv(da), d); }
BLEND_MODE(modulate) { return s*d; }
BLEND_MODE(multiply) { return s*inv(da) + d*inv(sa) + s*d; }
BLEND_MODE(plus_) { return min(s + d, 1.0f); } // We can clamp to either 1 or sa.
BLEND_MODE(screen) { return s + d - s*d; }
BLEND_MODE(xor_) { return s*inv(da) + d*inv(sa); }
#undef BLEND_MODE
@ -1180,17 +1181,6 @@ BLEND_MODE(softlight) {
}
#undef BLEND_MODE
STAGE(plus_, Ctx::None) {
// We don't clamp here in case the destination supports non-normalized colors.
r += dr;
g += dg;
b += db;
a += da;
// We do clamp alpha, because alpha > 1 is not something we're prepared to admit makes sense.
a = min(a, 1);
}
// We're basing our implemenation of non-separable blend modes on
// https://www.w3.org/TR/compositing-1/#blendingnonseparable.
// and
@ -2706,11 +2696,7 @@ STAGE_PP(move_dst_src, Ctx::None) {
BLEND_MODE(dstover) { return d + div255( s*inv(da) ); }
BLEND_MODE(modulate) { return div255( s*d ); }
BLEND_MODE(multiply) { return div255( s*inv(da) + d*inv(sa) + s*d ); }
BLEND_MODE(plus_) {
// N.B. we're clamping all channels to 255 (1.0) here due to format limitations.
// In the float code we only clamp alpha.
return min(s+d, 255);
}
BLEND_MODE(plus_) { return min(s+d, 255); }
BLEND_MODE(screen) { return s + d - div255( s*d ); }
BLEND_MODE(xor_) { return div255( s*inv(da) + d*inv(sa) ); }
#undef BLEND_MODE