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Harden linear gradients

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Ensure that the last offset == 1.0f when implict positions are used
(previously subject to float imprecision).

BUG=skia:5288,chromium:598484
R=reed@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1974463002

Review-Url: https://codereview.chromium.org/1974463002
This commit is contained in:
fmalita 2016-05-11 11:39:58 -07:00 committed by Commit bot
parent 87bf8f7d15
commit 748d620adc
2 changed files with 7 additions and 3 deletions
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2
src/effects/gradients/SkGradientShader.cpp
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@ -774,6 +774,8 @@ static bool valid_grad(const SkColor colors[], const SkScalar pos[], int count,
static void desc_init(SkGradientShaderBase::Descriptor* desc,
const SkColor colors[], const SkScalar pos[], int colorCount,
SkShader::TileMode mode, uint32_t flags, const SkMatrix* localMatrix) {
SkASSERT(colorCount > 1);
desc->fColors = colors;
desc->fPos = pos;
desc->fCount = colorCount;

8
src/effects/gradients/SkLinearGradient.cpp
View File

@ -99,7 +99,9 @@ SkLinearGradient::LinearGradientContext::LinearGradientContext(
: INHERITED(shader, ctx)
{
// setup for Sk4f
int count = shader.fColorCount;
const int count = shader.fColorCount;
SkASSERT(count > 1);
fRecs.setCount(count);
Rec* rec = fRecs.begin();
if (shader.fOrigPos) {
@ -114,16 +116,16 @@ SkLinearGradient::LinearGradientContext::LinearGradientContext(
rec[i].fPosScale = 0;
}
}
rec[count - 1].fPos = 1; // overwrite the last value just to be sure we end at 1.0
} else {
// no pos specified, so we compute evenly spaced values
const float scale = float(count - 1);
float invScale = 1.0f / scale;
const float invScale = 1.0f / scale;
for (int i = 0; i < count; ++i) {
rec[i].fPos = i * invScale;
rec[i].fPosScale = scale;
}
}
rec[count - 1].fPos = 1; // overwrite the last value just to be sure we end at 1.0
fApplyAlphaAfterInterp = true;
if ((shader.getGradFlags() & SkGradientShader::kInterpolateColorsInPremul_Flag) ||