SkGradientShaderBase::GradientShaderBaseContext::GradientShaderBaseContext(
const SkGradientShaderBase& shader, const ContextRec& rec)
: INHERITED(shader, rec)
#ifdef SK_SUPPORT_LEGACY_GRADIENT_DITHERING
, fDither(true)
#else
, fDither(rec.fPaint->isDither())
#endif
, fCache(shader.refCache(getPaintAlpha(), fDither))
{
const SkMatrix& inverse = this->getTotalInverse();
fDstToIndex.setConcat(shader.fPtsToUnit, inverse);
fDstToIndexProc = fDstToIndex.getMapXYProc();
fDstToIndexClass = (uint8_t)SkShader::Context::ComputeMatrixClass(fDstToIndex);
// now convert our colors in to PMColors
unsigned paintAlpha = this->getPaintAlpha();
fFlags = this->INHERITED::getFlags();
if (shader.fColorsAreOpaque && paintAlpha == 0xFF) {
fFlags |= kOpaqueAlpha_Flag;
}
// we can do span16 as long as our individual colors are opaque,
// regardless of the paint's alpha
if (shader.fColorsAreOpaque) {
fFlags |= kHasSpan16_Flag;
}
}
SkScalar SkPerlinNoiseShader::PerlinNoiseShaderContext::calculateTurbulenceValueForPoint(
int channel, StitchData& stitchData, const SkPoint& point) const {
const SkPerlinNoiseShader& perlinNoiseShader = static_cast<const SkPerlinNoiseShader&>(fShader);
if (perlinNoiseShader.fStitchTiles) {
// Set up TurbulenceInitial stitch values.
stitchData = fPaintingData->fStitchDataInit;
}
SkScalar turbulenceFunctionResult = 0;
SkPoint noiseVector(SkPoint::Make(SkScalarMul(point.x(), fPaintingData->fBaseFrequency.fX),
SkScalarMul(point.y(), fPaintingData->fBaseFrequency.fY)));
SkScalar ratio = SK_Scalar1;
for (int octave = 0; octave < perlinNoiseShader.fNumOctaves; ++octave) {
SkScalar noise = noise2D(channel, stitchData, noiseVector);
SkScalar numer = (perlinNoiseShader.fType == kFractalNoise_Type) ?
noise : SkScalarAbs(noise);
turbulenceFunctionResult += numer / ratio;
noiseVector.fX *= 2;
noiseVector.fY *= 2;
ratio *= 2;
if (perlinNoiseShader.fStitchTiles) {
// Update stitch values
stitchData.fWidth *= 2;
stitchData.fWrapX = stitchData.fWidth + kPerlinNoise;
stitchData.fHeight *= 2;
stitchData.fWrapY = stitchData.fHeight + kPerlinNoise;
}
}
// The value of turbulenceFunctionResult comes from ((turbulenceFunctionResult) + 1) / 2
// by fractalNoise and (turbulenceFunctionResult) by turbulence.
if (perlinNoiseShader.fType == kFractalNoise_Type) {
turbulenceFunctionResult =
SkScalarMul(turbulenceFunctionResult, SK_ScalarHalf) + SK_ScalarHalf;
}
if (channel == 3) { // Scale alpha by paint value
turbulenceFunctionResult *= SkIntToScalar(getPaintAlpha()) / 255;
}
// Clamp result
return SkScalarPin(turbulenceFunctionResult, 0, SK_Scalar1);
}
