GPU Gradients

src/effects/gradients/SkGradientShader.cpp

Index: src/effects/gradients/SkGradientShader.cpp
diff --git a/src/effects/gradients/SkGradientShader.cpp b/src/effects/gradients/SkGradientShader.cpp
index de43b69a2f70b78c1b4e3f667f9c357f2cf52b28..714ef72ba43abb794226f1c8a3c1224d3dbc60aa 100644
--- a/src/effects/gradients/SkGradientShader.cpp
+++ b/src/effects/gradients/SkGradientShader.cpp
@@ -832,28 +832,72 @@ GrGLGradientEffect::GrGLGradientEffect(const GrBackendEffectFactory& factory)
 
 GrGLGradientEffect::~GrGLGradientEffect() { }
 
-void GrGLGradientEffect::emitYCoordUniform(GrGLShaderBuilder* builder) {
-    fFSYUni = builder->addUniform(GrGLShaderBuilder::kFragment_ShaderType,
-                                  kFloat_GrSLType, "GradientYCoordFS");
+void GrGLGradientEffect::emitUniforms(GrGLShaderBuilder* builder, EffectKey key) {
+
+    if (GrGradientEffect::kTwo_ColorType == getColorType(key)) { // 2 Color case
+        fColorStartUni = builder->addUniform(GrGLShaderBuilder::kFragment_ShaderType,
+                                             kVec4f_GrSLType, "GradientStartColor");
+        fColorEndUni = builder->addUniform(GrGLShaderBuilder::kFragment_ShaderType,
+                                           kVec4f_GrSLType, "GradientEndColor");
+        
+    } else if (GrGradientEffect::kTwo_ColorType == getColorType(key)){ // 3 Color Case
+        fColorStartUni = builder->addUniform(GrGLShaderBuilder::kFragment_ShaderType,
+                                             kVec4f_GrSLType, "GradientStartColor");
+        fColorMidUni = builder->addUniform(GrGLShaderBuilder::kFragment_ShaderType,
+                                           kVec4f_GrSLType, "GradientMidColor");
+        fColorEndUni = builder->addUniform(GrGLShaderBuilder::kFragment_ShaderType,
+                                             kVec4f_GrSLType, "GradientEndColor");
+
+    } else { // if not a fast case
+        fFSYUni = builder->addUniform(GrGLShaderBuilder::kFragment_ShaderType,
+                                      kFloat_GrSLType, "GradientYCoordFS");
+    }
 }
 
 void GrGLGradientEffect::setData(const GrGLUniformManager& uman,
                                  const GrDrawEffect& drawEffect) {
+
     const GrGradientEffect& e = drawEffect.castEffect<GrGradientEffect>();
-    const GrTexture* texture = e.texture(0);
-    fEffectMatrix.setData(uman, e.getMatrix(), drawEffect, texture);
 
-    SkScalar yCoord = e.getYCoord();
-    if (yCoord != fCachedYCoord) {
-        uman.set1f(fFSYUni, yCoord);
-        fCachedYCoord = yCoord;
+
+    if (GrGradientEffect::kTwo_ColorType == e.getColorType()){
+        uman.set4f(fColorStartUni, 1.f, 1.f, 1.f, 1.f);
+        uman.set4f(fColorEndUni, 0.f, 0.f, 0.f, 1.f);
+
+    } else if (GrGradientEffect::kThree_ColorType == e.getColorType()){
+        uman.set4f(fColorStartUni, 1.f, 1.f, 1.f, 1.f);
+        uman.set4f(fColorMidUni, 1.f, 0.f, 0.f, 0.f);
+        uman.set4f(fColorEndUni, 1.f, 1.f, 1.f, 1.f);
+    } else {
+        const GrTexture* texture = e.texture(0);
+        fEffectMatrix.setData(uman, e.getMatrix(), drawEffect, texture);
+        
+        SkScalar yCoord = e.getYCoord();
+        if (yCoord != fCachedYCoord) {
+            uman.set1f(fFSYUni, yCoord);
+            fCachedYCoord = yCoord;
+        }
     }
 }
 
-GrGLEffect::EffectKey GrGLGradientEffect::GenMatrixKey(const GrDrawEffect& drawEffect) {
+
+GrGLEffect::EffectKey GrGLGradientEffect::GenBaseGradientKey(const GrDrawEffect& drawEffect) {
     const GrGradientEffect& e = drawEffect.castEffect<GrGradientEffect>();
-    const GrTexture* texture = e.texture(0);
-    return GrGLEffectMatrix::GenKey(e.getMatrix(), drawEffect, kCoordsType, texture);
+    const GrTexture* texture = NULL;
+    
+    if (e.getNumColors() > 3){
+        texture = e.texture(0);
+    }
+    
+    EffectKey key = GrGLEffectMatrix::GenKey(e.getMatrix(), drawEffect, kCoordsType, texture);
+
+    if (GrGradientEffect::kTwo_ColorType == e.getColorType()) {
+        key = key | kTwoColorKey;
+    } else if (GrGradientEffect::kThree_ColorType == e.getColorType()){
+        key = key | kThreeColorKey;
+    }
+
+    return key;
 }
 
 void GrGLGradientEffect::setupMatrix(GrGLShaderBuilder* builder,
@@ -868,21 +912,36 @@ void GrGLGradientEffect::setupMatrix(GrGLShaderBuilder* builder,
                                          vsVaryingType);
 }
 
-void GrGLGradientEffect::emitColorLookup(GrGLShaderBuilder* builder,
-                                         const char* gradientTValue,
-                                         const char* outputColor,
-                                         const char* inputColor,
-                                         const GrGLShaderBuilder::TextureSampler& sampler) {
-
-    builder->fsCodeAppendf("\tvec2 coord = vec2(%s, %s);\n",
-                           gradientTValue,
-                           builder->getUniformVariable(fFSYUni).c_str());
-    builder->fsCodeAppendf("\t%s = ", outputColor);
-    builder->appendTextureLookupAndModulate(GrGLShaderBuilder::kFragment_ShaderType,
-                                            inputColor,
-                                            sampler,
-                                            "coord");
-    builder->fsCodeAppend(";\n");
+void GrGLGradientEffect::emitColor(GrGLShaderBuilder* builder,
+                                   const char* gradientTValue,
+                                   EffectKey key,
+                                   const char* outputColor,
+                                   const char* inputColor,
+                                   const GrGLShaderBuilder::TextureSamplerArray& samplers) {
+    if (GrGradientEffect::kTwo_ColorType == getColorType(key)){
+        builder->fsCodeAppendf("\t%s = mix(%s, %s, %s);\n",
+                               outputColor,
+                               builder->getUniformVariable(fColorStartUni).c_str(),
+                               builder->getUniformVariable(fColorEndUni).c_str(),
+                               gradientTValue);
+    } else if (GrGradientEffect::kThree_ColorType == getColorType(key)){
+        //same as 2 color for now... causes bug from unused UNI

[dierk, 2013/08/13 19:50:18]

How to mix for 3 colors on the GPU? Is there a way to avoid doing a branch on
the GPU based on the t-value (as I imagine a branch would be much slower)?

[bsalomon, 2013/08/13 20:40:03]

I think this works, but not sure if it's faster than a branch:

oneMinus2T = 1 - 2t
color = clamp(oneMinus2T, 0, 1) * low + (1 - max(abs(oneMinus2T),1)) * mid +
clamp(-oneMinus2T, 0, 1) * high

clamp min and max may map to instructions. 

+        builder->fsCodeAppendf("\t%s = mix(%s, %s, %s);\n",
+                               outputColor,
+                               builder->getUniformVariable(fColorStartUni).c_str(),
+                               builder->getUniformVariable(fColorEndUni).c_str(),
+                               gradientTValue);
+    } else {
+        builder->fsCodeAppendf("\tvec2 coord = vec2(%s, %s);\n",
+                               gradientTValue,
+                               builder->getUniformVariable(fFSYUni).c_str());
+        builder->fsCodeAppendf("\t%s = ", outputColor);
+        builder->appendTextureLookupAndModulate(GrGLShaderBuilder::kFragment_ShaderType,
+                                                inputColor,
+                                                samplers[0],
+                                                "coord");
+        builder->fsCodeAppend(";\n");
+    }
 }
 
 /////////////////////////////////////////////////////////////////////
@@ -891,10 +950,6 @@ GrGradientEffect::GrGradientEffect(GrContext* ctx,
                                    const SkGradientShaderBase& shader,
                                    const SkMatrix& matrix,
                                    SkShader::TileMode tileMode) {
-    // TODO: check for simple cases where we don't need a texture:
-    //GradientInfo info;
-    //shader.asAGradient(&info);
-    //if (info.fColorCount == 2) { ...
 
     fMatrix = matrix;
 
@@ -903,36 +958,57 @@ GrGradientEffect::GrGradientEffect(GrContext* ctx,
 
     fIsOpaque = shader.isOpaque();
 
-    GrTextureStripAtlas::Desc desc;
-    desc.fWidth  = bitmap.width();
-    desc.fHeight = 32;
-    desc.fRowHeight = bitmap.height();
-    desc.fContext = ctx;
-    desc.fConfig = SkBitmapConfig2GrPixelConfig(bitmap.config());
-    fAtlas = GrTextureStripAtlas::GetAtlas(desc);
-    GrAssert(NULL != fAtlas);
-
-    // We always filter the gradient table. Each table is one row of a texture, so always y-clamp.
-    GrTextureParams params;
-    params.setFilterMode(GrTextureParams::kBilerp_FilterMode);
-    params.setTileModeX(tileMode);
-
-    fRow = fAtlas->lockRow(bitmap);
-    if (-1 != fRow) {
-        fYCoord = fAtlas->getYOffset(fRow) + SK_ScalarHalf *
-                  fAtlas->getVerticalScaleFactor();
-        fTextureAccess.reset(fAtlas->getTexture(), params);
-    } else {
-        GrTexture* texture = GrLockAndRefCachedBitmapTexture(ctx, bitmap, &params);
-        fTextureAccess.reset(texture, params);
-        fYCoord = SK_ScalarHalf;
+    // TODO: check for simple cases where we don't need a texture:
+    SkShader::GradientInfo info;
+    SkScalar pos[3] = {0};
+
+    info.fColorCount = 3;
+    info.fColors = NULL;
+    info.fColorOffsets = &pos[0];
+    shader.asAGradient(&info);
 
-        // Unlock immediately, this is not great, but we don't have a way of
-        // knowing when else to unlock it currently, so it may get purged from
-        // the cache, but it'll still be ref'd until it's no longer being used.
-        GrUnlockAndUnrefCachedBitmapTexture(texture);
+    if (2 == info.fColorCount) { // if 2 color
+        fRow = -1;
+        fNumColors = 2;
+
+    } else if (3 == info.fColorCount && (SkScalarAbs(pos[1] - 0.5) < 0.01)) { // if 3 color symmetric
+        fRow = -1;
+        fNumColors = 3;
+
+    } else {
+        fNumColors = 4; // if anything else use 4 as code for use texture instead
+        
+        GrTextureStripAtlas::Desc desc;
+        desc.fWidth  = bitmap.width();
+        desc.fHeight = 32;
+        desc.fRowHeight = bitmap.height();
+        desc.fContext = ctx;
+        desc.fConfig = SkBitmapConfig2GrPixelConfig(bitmap.config());
+        fAtlas = GrTextureStripAtlas::GetAtlas(desc);
+        GrAssert(NULL != fAtlas);
+
+        // We always filter the gradient table. Each table is one row of a texture, so always y-clamp.
+        GrTextureParams params;
+        params.setFilterMode(GrTextureParams::kBilerp_FilterMode);
+        params.setTileModeX(tileMode);
+
+        fRow = fAtlas->lockRow(bitmap);
+        if (-1 != fRow) {
+            fYCoord = fAtlas->getYOffset(fRow) + SK_ScalarHalf *
+            fAtlas->getVerticalScaleFactor();
+            fTextureAccess.reset(fAtlas->getTexture(), params);
+        } else {
+            GrTexture* texture = GrLockAndRefCachedBitmapTexture(ctx, bitmap, &params);
+            fTextureAccess.reset(texture, params);
+            fYCoord = SK_ScalarHalf;
+
+            // Unlock immediately, this is not great, but we don't have a way of
+            // knowing when else to unlock it currently, so it may get purged from
+            // the cache, but it'll still be ref'd until it's no longer being used.
+            GrUnlockAndUnrefCachedBitmapTexture(texture);
+        }
+        this->addTextureAccess(&fTextureAccess);
     }
-    this->addTextureAccess(&fTextureAccess);
 }
 
 GrGradientEffect::~GrGradientEffect() {
@@ -948,7 +1024,9 @@ bool GrGradientEffect::onIsEqual(const GrEffect& effect) const {
                 s.fTextureAccess.getParams().getTileModeX() &&
            this->useAtlas() == s.useAtlas() &&
            fYCoord == s.getYCoord() &&
-           fMatrix.cheapEqualTo(s.getMatrix());
+           fMatrix.cheapEqualTo(s.getMatrix())
+           && this->fNumColors == s.fNumColors;
+    // also check for colors of 2 / 3 gradients!
 }
 
 void GrGradientEffect::getConstantColorComponents(GrColor* color, uint32_t* validFlags) const {