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/*
* Copyright 2013 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "GrDistanceFieldTextureEffect.h"
#include "gl/GrGLEffect.h"
#include "gl/GrGLSL.h"
#include "gl/GrGLTexture.h"
#include "gl/GrGLVertexEffect.h"
#include "GrTBackendEffectFactory.h"
#include "GrTexture.h"
// The distance field is constructed as unsigned char values, so that the zero value is at 128,
// and the range is [-4, 4 - 1/255). Hence our multiplier is 8 - 1/32 and zero threshold is 128/255.
#define MULTIPLIER "7.96875"
#define THRESHOLD "0.50196078431"
class GrGLDistanceFieldTextureEffect : public GrGLVertexEffect {
public:
GrGLDistanceFieldTextureEffect(const GrBackendEffectFactory& factory,
const GrDrawEffect& drawEffect)
: INHERITED (factory)
, fTextureSize(SkSize::Make(-1.f,-1.f)) {}
virtual void emitCode(GrGLFullShaderBuilder* builder,
const GrDrawEffect& drawEffect,
EffectKey key,
const char* outputColor,
const char* inputColor,
const TransformedCoordsArray&,
const TextureSamplerArray& samplers) SK_OVERRIDE {
SkASSERT(1 == drawEffect.castEffect<GrDistanceFieldTextureEffect>().numVertexAttribs());
SkAssertResult(builder->enableFeature(GrGLShaderBuilder::kStandardDerivatives_GLSLFeature));
SkString fsCoordName;
const char* vsCoordName;
const char* fsCoordNamePtr;
builder->addVarying(kVec2f_GrSLType, "textureCoords", &vsCoordName, &fsCoordNamePtr);
fsCoordName = fsCoordNamePtr;
const char* attrName0 =
builder->getEffectAttributeName(drawEffect.getVertexAttribIndices()[0])->c_str();
builder->vsCodeAppendf("\t%s = %s;\n", vsCoordName, attrName0);
const char* textureSizeUniName = NULL;
fTextureSizeUni = builder->addUniform(GrGLShaderBuilder::kFragment_Visibility,
kVec2f_GrSLType, "TextureSize",
&textureSizeUniName);
builder->fsCodeAppend("\tvec4 texColor = ");
builder->fsAppendTextureLookup(samplers[0],
fsCoordName.c_str(),
kVec2f_GrSLType);
builder->fsCodeAppend(";\n");
builder->fsCodeAppend("\tfloat distance = " MULTIPLIER "*(texColor.r - " THRESHOLD ");\n");
// we adjust for the effect of the transformation on the distance by using
// the length of the gradient of the texture coordinates. We use st coordinates
// to ensure we're mapping 1:1 from texel space to pixel space.
builder->fsCodeAppendf("\tvec2 st = %s*%s;\n", fsCoordName.c_str(), textureSizeUniName);
builder->fsCodeAppend("\tvec2 Jdx = dFdx(st);\n");
builder->fsCodeAppend("\tvec2 Jdy = dFdy(st);\n");
builder->fsCodeAppend("\tvec2 st_grad = normalize(st);\n");
builder->fsCodeAppend("\tvec2 grad = vec2(st_grad.x*Jdx.x + st_grad.y*Jdy.x,\n");
builder->fsCodeAppend("\t st_grad.x*Jdx.y + st_grad.y*Jdy.y);\n");
// this gives us a smooth step across approximately one fragment
// (assuming a radius of the diagonal of the fragment, hence a factor of sqrt(2)/2)
builder->fsCodeAppend("\tfloat afwidth = 0.7071*length(grad);\n");
builder->fsCodeAppend("\tfloat val = smoothstep(-afwidth, afwidth, distance);\n");
builder->fsCodeAppendf("\t%s = %s;\n", outputColor,
(GrGLSLExpr4(inputColor) * GrGLSLExpr1("val")).c_str());
}
virtual void setData(const GrGLUniformManager& uman,
const GrDrawEffect& drawEffect) SK_OVERRIDE {
SkASSERT(fTextureSizeUni.isValid());
const GrDistanceFieldTextureEffect& distanceFieldEffect =
drawEffect.castEffect<GrDistanceFieldTextureEffect>();
if (distanceFieldEffect.getSize().width() != fTextureSize.width() ||
distanceFieldEffect.getSize().height() != fTextureSize.height()) {
fTextureSize = distanceFieldEffect.getSize();
uman.set2f(fTextureSizeUni,
distanceFieldEffect.getSize().width(),
distanceFieldEffect.getSize().height());
}
}
private:
GrGLUniformManager::UniformHandle fTextureSizeUni;
SkSize fTextureSize;
typedef GrGLVertexEffect INHERITED;
};
///////////////////////////////////////////////////////////////////////////////
GrDistanceFieldTextureEffect::GrDistanceFieldTextureEffect(GrTexture* texture,
const GrTextureParams& params,
const SkISize& size)
: fTextureAccess(texture, params)
, fSize(SkSize::Make(SkIntToScalar(size.width()), SkIntToScalar(size.height()))) {
this->addTextureAccess(&fTextureAccess);
this->addVertexAttrib(kVec2f_GrSLType);
}
bool GrDistanceFieldTextureEffect::onIsEqual(const GrEffect& other) const {
const GrDistanceFieldTextureEffect& cte = CastEffect<GrDistanceFieldTextureEffect>(other);
return fTextureAccess == cte.fTextureAccess;
}
void GrDistanceFieldTextureEffect::getConstantColorComponents(GrColor* color,
uint32_t* validFlags) const {
if ((*validFlags & kA_GrColorComponentFlag) && 0xFF == GrColorUnpackA(*color) &&
GrPixelConfigIsOpaque(this->texture(0)->config())) {
*validFlags = kA_GrColorComponentFlag;
} else {
*validFlags = 0;
}
}
const GrBackendEffectFactory& GrDistanceFieldTextureEffect::getFactory() const {
return GrTBackendEffectFactory<GrDistanceFieldTextureEffect>::getInstance();
}
///////////////////////////////////////////////////////////////////////////////
GR_DEFINE_EFFECT_TEST(GrDistanceFieldTextureEffect);
GrEffectRef* GrDistanceFieldTextureEffect::TestCreate(SkRandom* random,
GrContext*,
const GrDrawTargetCaps&,
GrTexture* textures[]) {
int texIdx = random->nextBool() ? GrEffectUnitTest::kSkiaPMTextureIdx :
GrEffectUnitTest::kAlphaTextureIdx;
static const SkShader::TileMode kTileModes[] = {
SkShader::kClamp_TileMode,
SkShader::kRepeat_TileMode,
SkShader::kMirror_TileMode,
};
SkShader::TileMode tileModes[] = {
kTileModes[random->nextULessThan(SK_ARRAY_COUNT(kTileModes))],
kTileModes[random->nextULessThan(SK_ARRAY_COUNT(kTileModes))],
};
GrTextureParams params(tileModes, random->nextBool() ? GrTextureParams::kBilerp_FilterMode :
GrTextureParams::kNone_FilterMode);
SkISize size = SkISize::Make(1024, 2048);
return GrDistanceFieldTextureEffect::Create(textures[texIdx], params, size);
}
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