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 #ifndef SkColorSpacePriv_DEFINED
8 #define SkColorSpacePriv_DEFINED
9
10 #include <math.h>
11
12 #include "SkColorSpace_Base.h"
13
14 #define SkColorSpacePrintf(...)
15
16 static constexpr float gSRGB_toXYZD50[] {
17 0.4360747f, 0.3850649f, 0.1430804f, // Rx, Gx, Bx
18 0.2225045f, 0.7168786f, 0.0606169f, // Ry, Gy, Gz
19 0.0139322f, 0.0971045f, 0.7141733f, // Rz, Gz, Bz
20 };
21
22 static constexpr float gAdobeRGB_toXYZD50[] {
23 0.6097559f, 0.2052401f, 0.1492240f, // Rx, Gx, Bx
24 0.3111242f, 0.6256560f, 0.0632197f, // Ry, Gy, Gz
25 0.0194811f, 0.0608902f, 0.7448387f, // Rz, Gz, Bz
26 };
27
28 static constexpr float gDCIP3_toXYZD50[] {
29 0.515102f, 0.291965f, 0.157153f, // Rx, Gx, Bx
30 0.241182f, 0.692236f, 0.0665819f, // Ry, Gy, Gz
31 -0.00104941f, 0.0418818f, 0.784378f, // Rz, Gz, Bz
32 };
33
34 static constexpr float gRec2020_toXYZD50[] {
35 0.673459f, 0.165661f, 0.125100f, // Rx, Gx, Bx
36 0.279033f, 0.675338f, 0.0456288f, // Ry, Gy, Gz
37 -0.00193139f, 0.0299794f, 0.797162f, // Rz, Gz, Bz
38 };
39
40 static constexpr SkColorSpaceTransferFn gSRGB_TransferFn =
41 { 2.4f, 1.0f / 1.055f, 0.055f / 1.055f, 1.0f / 12.92f, 0.04045f, 0.0f, 0.0f };
42
43 static constexpr SkColorSpaceTransferFn g2Dot2_TransferFn =
44 { 2.2f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f };
45
46 // gLinear_TransferFn.fD > 1.0f: Make sure that we use the linear segment of
47 // the transfer function even when the x-value is 1.0f.
48 static constexpr SkColorSpaceTransferFn gLinear_TransferFn =
49 { 0.0f, 0.0f, 0.0f, 1.0f, 1.0000001f, 0.0f, 0.0f };
50
51 static constexpr SkColorSpaceTransferFn gDCIP3_TransferFn =
52 { 2.399994f, 0.947998047f, 0.0520019531f, 0.0769958496f, 0.0390014648f, 0.0f, 0.0f };
53
to_xyz_d50(SkMatrix44 * toXYZD50,SkColorSpace::Gamut gamut)54 static inline void to_xyz_d50(SkMatrix44* toXYZD50, SkColorSpace::Gamut gamut) {
55 switch (gamut) {
56 case SkColorSpace::kSRGB_Gamut:
57 toXYZD50->set3x3RowMajorf(gSRGB_toXYZD50);
58 break;
59 case SkColorSpace::kAdobeRGB_Gamut:
60 toXYZD50->set3x3RowMajorf(gAdobeRGB_toXYZD50);
61 break;
62 case SkColorSpace::kDCIP3_D65_Gamut:
63 toXYZD50->set3x3RowMajorf(gDCIP3_toXYZD50);
64 break;
65 case SkColorSpace::kRec2020_Gamut:
66 toXYZD50->set3x3RowMajorf(gRec2020_toXYZD50);
67 break;
68 }
69 }
70
color_space_almost_equal(float a,float b)71 static inline bool color_space_almost_equal(float a, float b) {
72 return SkTAbs(a - b) < 0.01f;
73 }
74
75 // Let's use a stricter version for transfer functions. Worst case, these are encoded
76 // in ICC format, which offers 16-bits of fractional precision.
transfer_fn_almost_equal(float a,float b)77 static inline bool transfer_fn_almost_equal(float a, float b) {
78 return SkTAbs(a - b) < 0.001f;
79 }
80
is_zero_to_one(float v)81 static inline bool is_zero_to_one(float v) {
82 // Because we allow a value just barely larger than 1, the client can use an
83 // entirely linear transfer function.
84 return (0.0f <= v) && (v <= nextafterf(1.0f, 2.0f));
85 }
86
is_valid_transfer_fn(const SkColorSpaceTransferFn & coeffs)87 static inline bool is_valid_transfer_fn(const SkColorSpaceTransferFn& coeffs) {
88 if (SkScalarIsNaN(coeffs.fA) || SkScalarIsNaN(coeffs.fB) ||
89 SkScalarIsNaN(coeffs.fC) || SkScalarIsNaN(coeffs.fD) ||
90 SkScalarIsNaN(coeffs.fE) || SkScalarIsNaN(coeffs.fF) ||
91 SkScalarIsNaN(coeffs.fG))
92 {
93 return false;
94 }
95
96 if (!is_zero_to_one(coeffs.fD)) {
97 return false;
98 }
99
100 if (coeffs.fD == 0.0f) {
101 // Y = (aX + b)^g + e for always
102 if (0.0f == coeffs.fA || 0.0f == coeffs.fG) {
103 SkColorSpacePrintf("A or G is zero, constant transfer function "
104 "is nonsense");
105 return false;
106 }
107 }
108
109 if (coeffs.fD >= 1.0f) {
110 // Y = cX + f for always
111 if (0.0f == coeffs.fC) {
112 SkColorSpacePrintf("C is zero, constant transfer function is "
113 "nonsense");
114 return false;
115 }
116 }
117
118 if ((0.0f == coeffs.fA || 0.0f == coeffs.fG) && 0.0f == coeffs.fC) {
119 SkColorSpacePrintf("A or G, and C are zero, constant transfer function "
120 "is nonsense");
121 return false;
122 }
123
124 if (coeffs.fC < 0.0f) {
125 SkColorSpacePrintf("Transfer function must be increasing");
126 return false;
127 }
128
129 if (coeffs.fA < 0.0f || coeffs.fG < 0.0f) {
130 SkColorSpacePrintf("Transfer function must be positive or increasing");
131 return false;
132 }
133
134 return true;
135 }
136
is_almost_srgb(const SkColorSpaceTransferFn & coeffs)137 static inline bool is_almost_srgb(const SkColorSpaceTransferFn& coeffs) {
138 return transfer_fn_almost_equal(gSRGB_TransferFn.fA, coeffs.fA) &&
139 transfer_fn_almost_equal(gSRGB_TransferFn.fB, coeffs.fB) &&
140 transfer_fn_almost_equal(gSRGB_TransferFn.fC, coeffs.fC) &&
141 transfer_fn_almost_equal(gSRGB_TransferFn.fD, coeffs.fD) &&
142 transfer_fn_almost_equal(gSRGB_TransferFn.fE, coeffs.fE) &&
143 transfer_fn_almost_equal(gSRGB_TransferFn.fF, coeffs.fF) &&
144 transfer_fn_almost_equal(gSRGB_TransferFn.fG, coeffs.fG);
145 }
146
is_almost_2dot2(const SkColorSpaceTransferFn & coeffs)147 static inline bool is_almost_2dot2(const SkColorSpaceTransferFn& coeffs) {
148 return transfer_fn_almost_equal(1.0f, coeffs.fA) &&
149 transfer_fn_almost_equal(0.0f, coeffs.fB) &&
150 transfer_fn_almost_equal(0.0f, coeffs.fE) &&
151 transfer_fn_almost_equal(2.2f, coeffs.fG) &&
152 coeffs.fD <= 0.0f;
153 }
154
is_almost_linear(const SkColorSpaceTransferFn & coeffs)155 static inline bool is_almost_linear(const SkColorSpaceTransferFn& coeffs) {
156 // OutputVal = InputVal ^ 1.0f
157 const bool linearExp =
158 transfer_fn_almost_equal(1.0f, coeffs.fA) &&
159 transfer_fn_almost_equal(0.0f, coeffs.fB) &&
160 transfer_fn_almost_equal(0.0f, coeffs.fE) &&
161 transfer_fn_almost_equal(1.0f, coeffs.fG) &&
162 coeffs.fD <= 0.0f;
163
164 // OutputVal = 1.0f * InputVal
165 const bool linearFn =
166 transfer_fn_almost_equal(1.0f, coeffs.fC) &&
167 transfer_fn_almost_equal(0.0f, coeffs.fF) &&
168 coeffs.fD >= 1.0f;
169
170 return linearExp || linearFn;
171 }
172
value_to_parametric(SkColorSpaceTransferFn * coeffs,float exponent)173 static inline void value_to_parametric(SkColorSpaceTransferFn* coeffs, float exponent) {
174 coeffs->fA = 1.0f;
175 coeffs->fB = 0.0f;
176 coeffs->fC = 0.0f;
177 coeffs->fD = 0.0f;
178 coeffs->fE = 0.0f;
179 coeffs->fF = 0.0f;
180 coeffs->fG = exponent;
181 }
182
named_to_parametric(SkColorSpaceTransferFn * coeffs,SkGammaNamed gammaNamed)183 static inline bool named_to_parametric(SkColorSpaceTransferFn* coeffs,
184 SkGammaNamed gammaNamed) {
185 switch (gammaNamed) {
186 case kSRGB_SkGammaNamed:
187 *coeffs = gSRGB_TransferFn;
188 return true;
189 case k2Dot2Curve_SkGammaNamed:
190 *coeffs = g2Dot2_TransferFn;
191 return true;
192 case kLinear_SkGammaNamed:
193 *coeffs = gLinear_TransferFn;
194 return true;
195 default:
196 return false;
197 }
198 }
199 #endif // SkColorSpacePriv_DEFINED
200