1 /* 2 * Copyright 2012 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 #ifndef GrConfigConversionEffect_DEFINED 9 #define GrConfigConversionEffect_DEFINED 10 11 #include "GrSingleTextureEffect.h" 12 13 class GrProcessorStage; 14 class GrGLConfigConversionEffect; 15 16 /** 17 * This class is used to perform config conversions. Clients may want to read/write data that is 18 * unpremultiplied. Also on some systems reading/writing BGRA or RGBA is faster. In those cases we 19 * read/write using the faster path and perform an R/B swap in the shader if the client data is in 20 * the slower config. 21 */ 22 class GrConfigConversionEffect : public GrSingleTextureEffect { 23 public: 24 /** 25 * The PM->UPM or UPM->PM conversions to apply. 26 */ 27 enum PMConversion { 28 kNone_PMConversion = 0, 29 kMulByAlpha_RoundUp_PMConversion, 30 kMulByAlpha_RoundDown_PMConversion, 31 kDivByAlpha_RoundUp_PMConversion, 32 kDivByAlpha_RoundDown_PMConversion, 33 34 kPMConversionCnt 35 }; 36 37 // Installs an effect in the GrProcessorStage to perform a config conversion. 38 static const GrFragmentProcessor* Create(GrTexture*, bool swapRedAndBlue, PMConversion, 39 const SkMatrix&); 40 41 static const char* Name() { return "Config Conversion"; } 42 typedef GrGLConfigConversionEffect GLProcessor; 43 44 virtual const GrBackendFragmentProcessorFactory& getFactory() const SK_OVERRIDE; 45 46 virtual void getConstantColorComponents(GrColor* color, uint32_t* validFlags) const SK_OVERRIDE; 47 48 bool swapsRedAndBlue() const { return fSwapRedAndBlue; } 49 PMConversion pmConversion() const { return fPMConversion; } 50 51 // This function determines whether it is possible to choose PM->UPM and UPM->PM conversions 52 // for which in any PM->UPM->PM->UPM sequence the two UPM values are the same. This means that 53 // if pixels are read back to a UPM buffer, written back to PM to the GPU, and read back again 54 // both reads will produce the same result. This test is quite expensive and should not be run 55 // multiple times for a given context. 56 static void TestForPreservingPMConversions(GrContext* context, 57 PMConversion* PMToUPMRule, 58 PMConversion* UPMToPMRule); 59 60 private: 61 GrConfigConversionEffect(GrTexture*, 62 bool swapRedAndBlue, 63 PMConversion pmConversion, 64 const SkMatrix& matrix); 65 66 virtual bool onIsEqual(const GrProcessor&) const SK_OVERRIDE; 67 68 bool fSwapRedAndBlue; 69 PMConversion fPMConversion; 70 71 GR_DECLARE_FRAGMENT_PROCESSOR_TEST; 72 73 typedef GrSingleTextureEffect INHERITED; 74 }; 75 76 #endif 77