Gamma correction for distance field text.

src/gpu/effects/GrDistanceFieldTextureEffect.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrDistanceFieldTextureEffect_DEFINED
 #define GrDistanceFieldTextureEffect_DEFINED
 
 #include "GrEffect.h"
 #include "GrVertexEffect.h"
 
 class GrGLDistanceFieldTextureEffect;
 class GrGLDistanceFieldLCDTextureEffect;
 
 /**
  * The output color of this effect is a modulation of the input color and a sample from a
  * distance field texture (using a smoothed step function near 0.5).
  * It allows explicit specification of the filtering and wrap modes (GrTextureParams). The input
- * coords are a custom attribute.
+ * coords are a custom attribute. Gamma correction is handled via a texture LUT.
  */
 class GrDistanceFieldTextureEffect : public GrVertexEffect {
 public:
-    static GrEffectRef* Create(GrTexture* tex, const GrTextureParams& params, bool similarity) {
-        AutoEffectUnref effect(SkNEW_ARGS(GrDistanceFieldTextureEffect, (tex, params, similarity)));
+#ifdef SK_GAMMA_APPLY_TO_A8
+    static GrEffectRef* Create(GrTexture* tex, const GrTextureParams& params,
+                               GrTexture* gamma, const GrTextureParams& gammaParams, float lum,
+                               bool similarity) {
+        AutoEffectUnref effect(SkNEW_ARGS(GrDistanceFieldTextureEffect, (tex, params,
+                                                                         gamma, gammaParams, lum,
+                                                                         similarity)));
+#else
+    static GrEffectRef* Create(GrTexture* tex, const GrTextureParams& params,
+                               bool similarity) {
+        AutoEffectUnref effect(SkNEW_ARGS(GrDistanceFieldTextureEffect, (tex, params,
+                                                                         similarity)));
+#endif
         return CreateEffectRef(effect);
     }
 
     virtual ~GrDistanceFieldTextureEffect() {}
 
     static const char* Name() { return "DistanceFieldTexture"; }
 
     virtual void getConstantColorComponents(GrColor* color, uint32_t* validFlags) const SK_OVERRIDE;
+#ifdef SK_GAMMA_APPLY_TO_A8
+    float getLuminance() const { return fLuminance; }
+#endif
     bool isSimilarity() const { return fIsSimilarity; }
 
     typedef GrGLDistanceFieldTextureEffect GLEffect;
 
     virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;
 
 private:
     GrDistanceFieldTextureEffect(GrTexture* texture, const GrTextureParams& params,
+#ifdef SK_GAMMA_APPLY_TO_A8
+                                 GrTexture* gamma, const GrTextureParams& gammaParams, float lum,
+#endif
                                  bool uniformScale);
 
     virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;
 
     GrTextureAccess fTextureAccess;
+#ifdef SK_GAMMA_APPLY_TO_A8
+    GrTextureAccess fGammaTextureAccess;
+    float           fLuminance;
+#endif
     bool            fIsSimilarity;
 
     GR_DECLARE_EFFECT_TEST;
 
     typedef GrVertexEffect INHERITED;
 };
 
 /**
  * The output color of this effect is a modulation of the input color and samples from a
  * distance field texture (using a smoothed step function near 0.5), adjusted for LCD displays.
  * It allows explicit specification of the filtering and wrap modes (GrTextureParams). The input
- * coords are a custom attribute.
+ * coords are a custom attribute. Gamma correction is handled via a texture LUT.
  */
 class GrDistanceFieldLCDTextureEffect : public GrVertexEffect {
 public:
     static GrEffectRef* Create(GrTexture* tex, const GrTextureParams& params,
+                               GrTexture* gamma, const GrTextureParams& gammaParams, 
+                               SkColor textColor,
                                bool uniformScale, bool useBGR) {
         AutoEffectUnref effect(SkNEW_ARGS(GrDistanceFieldLCDTextureEffect,
-                                          (tex, params, uniformScale, useBGR)));
+                                          (tex, params, gamma, gammaParams, textColor, uniformScale,
+                                           useBGR)));
         return CreateEffectRef(effect);
     }
 
     virtual ~GrDistanceFieldLCDTextureEffect() {}
 
     static const char* Name() { return "DistanceFieldLCDTexture"; }
 
     virtual void getConstantColorComponents(GrColor* color, uint32_t* validFlags) const SK_OVERRIDE;
+    GrColor getTextColor() const { return fTextColor; }
     bool isUniformScale() const { return fUniformScale; }
     bool useBGR() const { return fUseBGR; }
 
     typedef GrGLDistanceFieldLCDTextureEffect GLEffect;
 
     virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;
 
 private:
     GrDistanceFieldLCDTextureEffect(GrTexture* texture, const GrTextureParams& params,
+                                    GrTexture* gamma, const GrTextureParams& gammaParams,
+                                    SkColor textColor,
                                     bool uniformScale, bool useBGR);
 
     virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;
 
     GrTextureAccess fTextureAccess;
+    GrTextureAccess fGammaTextureAccess;
+    GrColor         fTextColor;
     bool            fUniformScale;
     bool            fUseBGR;
 
     GR_DECLARE_EFFECT_TEST;
 
     typedef GrVertexEffect INHERITED;
 };
 
-
 #endif