src/third_party/skia/src/effects/SkLumaColorFilter.cpp

   1 /*
   2  * Copyright 2013 Google Inc.
   3  *
   4  * Use of this source code is governed by a BSD-style license that can be
   5  * found in the LICENSE file.
   6  */
   7
   8 #include "SkLumaColorFilter.h"
   9
  10 #include "SkColorPriv.h"
  11 #include "SkString.h"
  12
  13 #if SK_SUPPORT_GPU
  14 #include "gl/GrGLProcessor.h"
  15 #include "gl/builders/GrGLProgramBuilder.h"
  16 #include "GrContext.h"
  17 #include "GrTBackendProcessorFactory.h"
  18 #endif
  19
  20 void SkLumaColorFilter::filterSpan(const SkPMColor src[], int count,
  21                                    SkPMColor dst[]) const {
  22     for (int i = 0; i < count; ++i) {
  23         SkPMColor c = src[i];
  24
  25         /*
  26          * While LuminanceToAlpha is defined to operate on un-premultiplied
  27          * inputs, due to the final alpha scaling it can be computed based on
  28          * premultipled components:
  29          *
  30          *   LumA = (k1 * r / a + k2 * g / a + k3 * b / a) * a
  31          *   LumA = (k1 * r + k2 * g + k3 * b)
  32          */
  33         unsigned luma = SkComputeLuminance(SkGetPackedR32(c),
  34                                            SkGetPackedG32(c),
  35                                            SkGetPackedB32(c));
  36         dst[i] = SkPackARGB32(luma, 0, 0, 0);
  37     }
  38 }
  39
  40 SkColorFilter* SkLumaColorFilter::Create() {
  41     return SkNEW(SkLumaColorFilter);
  42 }
  43
  44 SkLumaColorFilter::SkLumaColorFilter() : INHERITED() {}
  45
  46 #ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
  47 SkLumaColorFilter::SkLumaColorFilter(SkReadBuffer& buffer) : INHERITED(buffer) {}
  48 #endif
  49
  50 SkFlattenable* SkLumaColorFilter::CreateProc(SkReadBuffer&) {
  51     return SkNEW(SkLumaColorFilter);
  52 }
  53
  54 void SkLumaColorFilter::flatten(SkWriteBuffer&) const {}
  55
  56 #ifndef SK_IGNORE_TO_STRING
  57 void SkLumaColorFilter::toString(SkString* str) const {
  58     str->append("SkLumaColorFilter ");
  59 }
  60 #endif
  61
  62 #if SK_SUPPORT_GPU
  63 class LumaColorFilterEffect : public GrFragmentProcessor {
  64 public:
  65     static GrFragmentProcessor* Create() {
  66         GR_CREATE_STATIC_FRAGMENT_PROCESSOR(gLumaEffect, LumaColorFilterEffect, ());
  67         return SkRef(gLumaEffect);
  68     }
  69
  70     static const char* Name() { return "Luminance-to-Alpha"; }
  71
  72     virtual const GrBackendFragmentProcessorFactory& getFactory() const SK_OVERRIDE {
  73         return GrTBackendFragmentProcessorFactory<LumaColorFilterEffect>::getInstance();
  74     }
  75
  76     virtual void getConstantColorComponents(GrColor* color,
  77                                             uint32_t* validFlags) const SK_OVERRIDE {
  78         // The output is always black.
  79         *color = GrColorPackRGBA(0, 0, 0, GrColorUnpackA(*color));
  80         *validFlags = kRGB_GrColorComponentFlags;
  81     }
  82
  83     class GLProcessor : public GrGLFragmentProcessor {
  84     public:
  85         GLProcessor(const GrBackendProcessorFactory& factory,
  86                     const GrProcessor&)
  87         : INHERITED(factory) {
  88         }
  89
  90         static void GenKey(const GrProcessor&, const GrGLCaps&, GrProcessorKeyBuilder* b) {}
  91
  92         virtual void emitCode(GrGLProgramBuilder* builder,
  93                               const GrFragmentProcessor&,
  94                               const GrProcessorKey&,
  95                               const char* outputColor,
  96                               const char* inputColor,
  97                               const TransformedCoordsArray&,
  98                               const TextureSamplerArray&) SK_OVERRIDE {
  99             if (NULL == inputColor) {
 100                 inputColor = "vec4(1)";
 101             }
 102
 103             GrGLFragmentShaderBuilder* fsBuilder = builder->getFragmentShaderBuilder();
 104             fsBuilder->codeAppendf("\tfloat luma = dot(vec3(%f, %f, %f), %s.rgb);\n",
 105                                    SK_ITU_BT709_LUM_COEFF_R,
 106                                    SK_ITU_BT709_LUM_COEFF_G,
 107                                    SK_ITU_BT709_LUM_COEFF_B,
 108                                    inputColor);
 109             fsBuilder->codeAppendf("\t%s = vec4(0, 0, 0, luma);\n",
 110                                    outputColor);
 111
 112         }
 113
 114     private:
 115         typedef GrGLFragmentProcessor INHERITED;
 116     };
 117
 118 private:
 119     virtual bool onIsEqual(const GrProcessor&) const SK_OVERRIDE {
 120         return true;
 121     }
 122 };
 123
 124 GrFragmentProcessor* SkLumaColorFilter::asFragmentProcessor(GrContext*) const {
 125     return LumaColorFilterEffect::Create();
 126 }
 127 #endif