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fix composeshader to respect the paint's alpha

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BUG=skia:
R=scroggo@google.com

Author: reed@google.com

Review URL: https://codereview.chromium.org/265163008

git-svn-id: http://skia.googlecode.com/svn/trunk@14569 2bbb7eff-a529-9590-31e7-b0007b416f81
This commit is contained in:
commit-bot@chromium.org 2014-05-05 16:45:01 +00:00
parent 3253f83605
commit 1ab536f161
1 changed files with 12 additions and 5 deletions
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17
src/core/SkComposeShader.cpp
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@ -100,20 +100,23 @@ SkShader::Context* SkComposeShader::createContext(const ContextRec& rec, void* s
return NULL;
}
// TODO : must fix this to not "cheat" and modify fPaint
SkAutoAlphaRestore restore(const_cast<SkPaint*>(rec.fPaint), 0xFF);
char* aStorage = (char*) storage + sizeof(ComposeShaderContext);
char* bStorage = aStorage + fShaderA->contextSize();
// we preconcat our localMatrix (if any) with the device matrix
// before calling our sub-shaders
SkMatrix tmpM;
tmpM.setConcat(*rec.fMatrix, this->getLocalMatrix());
// Our sub-shaders need to see opaque, so by combining them we don't double-alphatize the
// result. ComposeShader itself will respect the alpha, and post-apply it after calling the
// sub-shaders.
SkPaint opaquePaint(*rec.fPaint);
opaquePaint.setAlpha(0xFF);
ContextRec newRec(rec);
newRec.fMatrix = &tmpM;
newRec.fPaint = &opaquePaint;
SkShader::Context* contextA = fShaderA->createContext(newRec, aStorage);
SkShader::Context* contextB = fShaderB->createContext(newRec, bStorage);
@ -148,6 +151,10 @@ void SkComposeShader::ComposeShaderContext::shadeSpan(int x, int y, SkPMColor re
SkXfermode* mode = static_cast<const SkComposeShader&>(fShader).fMode;
unsigned scale = SkAlpha255To256(this->getPaintAlpha());
#ifdef SK_BUILD_FOR_ANDROID
scale = 256; // ugh -- maintain old bug/behavior for now
#endif
SkPMColor tmp[TMP_COLOR_COUNT];
if (NULL == mode) { // implied SRC_OVER
@ -188,7 +195,7 @@ void SkComposeShader::ComposeShaderContext::shadeSpan(int x, int y, SkPMColor re
shaderContextB->shadeSpan(x, y, tmp, n);
mode->xfer32(result, tmp, n, NULL);
if (256 == scale) {
if (256 != scale) {
for (int i = 0; i < n; i++) {
result[i] = SkAlphaMulQ(result[i], scale);
}