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bicubic in skvm image shader

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Change-Id: Ie7f926969466aeaaca46ba2ee7645dec2ce38696
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/262891
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
This commit is contained in:
Mike Klein 2020-01-07 13:19:39 -06:00 committed by Skia Commit-Bot
parent 1c16b43033
commit c89c1993e3
1 changed files with 24 additions and 2 deletions
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26
src/shaders/SkImageShader.cpp
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@ -791,9 +791,31 @@ bool SkImageShader::onProgram(skvm::Builder* p,
wy[1] = fy;
D = 2;
} else {
// TODO: bicubic weights
// See GrCubicEffect for details of these weights.
auto near = [&](skvm::F32 t) {
// 1/18 + 9/18t + 27/18t^2 - 21/18t^3 == t ( t ( -21/18t + 27/18) + 9/18) + 1/18
return p->mad(t,
p->mad(t,
p->mad(t, p->splat(-21/18.0f),
p->splat( 27/18.0f)),
p->splat( 9/18.0f)),
p->splat( 1/18.0f));
};
auto far = [&](skvm::F32 t) {
// 0/18 + 0/18*t - 6/18t^2 + 7/18t^3 == t^2 (7/18t - 6/18)
return p->mul(p->mul(t,t), p->mad(t, p->splat( 7/18.0f),
p->splat(-6/18.0f)));
};
wx[0] = far (p->sub(p->splat(1.0f), fx));
wx[1] = near(p->sub(p->splat(1.0f), fx));
wx[2] = near( fx );
wx[3] = far ( fx );
wy[0] = far (p->sub(p->splat(1.0f), fy));
wy[1] = near(p->sub(p->splat(1.0f), fy));
wy[2] = near( fy );
wy[3] = far ( fy );
D = 4;
return false;
}
*r = *g = *b = *a = p->splat(0.0f);