1 /* 2 * Copyright 2016 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 SkColorSpace_DEFINED 9 #define SkColorSpace_DEFINED 10 11 #include "SkMatrix44.h" 12 #include "SkRefCnt.h" 13 14 class SkData; 15 16 /** 17 * Describes a color gamut with primaries and a white point. 18 */ 19 struct SK_API SkColorSpacePrimaries { 20 float fRX, fRY; 21 float fGX, fGY; 22 float fBX, fBY; 23 float fWX, fWY; 24 25 /** 26 * Convert primaries and a white point to a toXYZD50 matrix, the preferred color gamut 27 * representation of SkColorSpace. 28 */ 29 bool toXYZD50(SkMatrix44* toXYZD50) const; 30 }; 31 32 /** 33 * Contains the coefficients for a common transfer function equation, specified as 34 * a transformation from a curved space to linear. 35 * 36 * LinearVal = C*InputVal + F , for 0.0f <= InputVal < D 37 * LinearVal = (A*InputVal + B)^G + E, for D <= InputVal <= 1.0f 38 * 39 * Function is undefined if InputVal is not in [ 0.0f, 1.0f ]. 40 * Resulting LinearVals must be in [ 0.0f, 1.0f ]. 41 * Function must be positive and increasing. 42 */ 43 struct SK_API SkColorSpaceTransferFn { 44 float fG; 45 float fA; 46 float fB; 47 float fC; 48 float fD; 49 float fE; 50 float fF; 51 52 /** 53 * Produces a new parametric transfer function equation that is the mathematical inverse of 54 * this one. 55 */ 56 SkColorSpaceTransferFn invert() const; 57 }; 58 59 class SK_API SkColorSpace : public SkRefCnt { 60 public: 61 62 /** 63 * Create the sRGB color space. 64 */ 65 static sk_sp<SkColorSpace> MakeSRGB(); 66 67 /** 68 * Colorspace with the sRGB primaries, but a linear (1.0) gamma. Commonly used for 69 * half-float surfaces, and high precision individual colors (gradient stops, etc...) 70 */ 71 static sk_sp<SkColorSpace> MakeSRGBLinear(); 72 73 enum RenderTargetGamma : uint8_t { 74 kLinear_RenderTargetGamma, 75 76 /** 77 * Transfer function is the canonical sRGB curve, which has a short linear segment 78 * followed by a 2.4f exponential. 79 */ 80 kSRGB_RenderTargetGamma, 81 }; 82 83 enum Gamut { 84 kSRGB_Gamut, 85 kAdobeRGB_Gamut, 86 kDCIP3_D65_Gamut, 87 kRec2020_Gamut, 88 }; 89 90 /** 91 * Create an SkColorSpace from a transfer function and a color gamut. 92 * 93 * Transfer function can be specified as an enum or as the coefficients to an equation. 94 * Gamut can be specified as an enum or as the matrix transformation to XYZ D50. 95 */ 96 static sk_sp<SkColorSpace> MakeRGB(RenderTargetGamma gamma, Gamut gamut); 97 static sk_sp<SkColorSpace> MakeRGB(RenderTargetGamma gamma, const SkMatrix44& toXYZD50); 98 static sk_sp<SkColorSpace> MakeRGB(const SkColorSpaceTransferFn& coeffs, Gamut gamut); 99 static sk_sp<SkColorSpace> MakeRGB(const SkColorSpaceTransferFn& coeffs, 100 const SkMatrix44& toXYZD50); 101 102 /** 103 * Create an SkColorSpace from an ICC profile. 104 */ 105 static sk_sp<SkColorSpace> MakeICC(const void*, size_t); 106 107 /** 108 * Returns true if the color space gamma is near enough to be approximated as sRGB. 109 * This includes the canonical sRGB transfer function as well as a 2.2f exponential 110 * transfer function. 111 */ 112 bool gammaCloseToSRGB() const; 113 114 /** 115 * Returns true if the color space gamma is linear. 116 */ 117 bool gammaIsLinear() const; 118 119 /** 120 * If the transfer function can be represented as coefficients to the standard 121 * equation, returns true and sets |fn| to the proper values. 122 * 123 * If not, returns false. 124 */ 125 bool isNumericalTransferFn(SkColorSpaceTransferFn* fn) const; 126 127 /** 128 * Returns true and sets |toXYZD50| if the color gamut can be described as a matrix. 129 * Returns false otherwise. 130 */ 131 bool toXYZD50(SkMatrix44* toXYZD50) const; 132 133 /** 134 * Returns true if the color space is sRGB. 135 * Returns false otherwise. 136 * 137 * This allows a little bit of tolerance, given that we might see small numerical error 138 * in some cases: converting ICC fixed point to float, converting white point to D50, 139 * rounding decisions on transfer function and matrix. 140 * 141 * This does not consider a 2.2f exponential transfer function to be sRGB. While these 142 * functions are similar (and it is sometimes useful to consider them together), this 143 * function checks for logical equality. 144 */ 145 bool isSRGB() const; 146 147 /** 148 * Returns nullptr on failure. Fails when we fallback to serializing ICC data and 149 * the data is too large to serialize. 150 */ 151 sk_sp<SkData> serialize() const; 152 153 /** 154 * If |memory| is nullptr, returns the size required to serialize. 155 * Otherwise, serializes into |memory| and returns the size. 156 */ 157 size_t writeToMemory(void* memory) const; 158 159 static sk_sp<SkColorSpace> Deserialize(const void* data, size_t length); 160 161 /** 162 * If both are null, we return true. If one is null and the other is not, we return false. 163 * If both are non-null, we do a deeper compare. 164 */ 165 static bool Equals(const SkColorSpace* src, const SkColorSpace* dst); 166 167 protected: 168 SkColorSpace() {} 169 }; 170 171 enum class SkTransferFunctionBehavior { 172 /** 173 * Converts to a linear space before premultiplying, unpremultiplying, or blending. 174 */ 175 kRespect, 176 177 /** 178 * Premultiplies, unpremultiplies, and blends ignoring the transfer function. Pixels are 179 * treated as if they are linear, regardless of their transfer function encoding. 180 */ 181 kIgnore, 182 }; 183 184 #endif 185
