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 "include/core/SkColorSpace.h"
13 #include "include/private/SkFixed.h"
14
15 #define SkColorSpacePrintf(...)
16
17 // A gamut narrower than sRGB, useful for testing.
18 static constexpr skcms_Matrix3x3 gNarrow_toXYZD50 = {{
19 { 0.190974f, 0.404865f, 0.368380f },
20 { 0.114746f, 0.582937f, 0.302318f },
21 { 0.032925f, 0.153615f, 0.638669f },
22 }};
23
color_space_almost_equal(float a,float b)24 static inline bool color_space_almost_equal(float a, float b) {
25 return SkTAbs(a - b) < 0.01f;
26 }
27
28 // Let's use a stricter version for transfer functions. Worst case, these are encoded
29 // in ICC format, which offers 16-bits of fractional precision.
transfer_fn_almost_equal(float a,float b)30 static inline bool transfer_fn_almost_equal(float a, float b) {
31 return SkTAbs(a - b) < 0.001f;
32 }
33
34 // NOTE: All of this logic is copied from skcms.cc, and needs to be kept in sync.
35
36 // Most transfer functions we work with are sRGBish.
37 // For exotic HDR transfer functions, we encode them using a tf.g that makes no sense,
38 // and repurpose the other fields to hold the parameters of the HDR functions.
39 enum TFKind { Bad_TF, sRGBish_TF, PQish_TF, HLGish_TF, HLGinvish_TF };
40
classify_transfer_fn(const skcms_TransferFunction & tf)41 static inline TFKind classify_transfer_fn(const skcms_TransferFunction& tf) {
42 if (tf.g < 0 && (int)tf.g == tf.g) {
43 // TODO: sanity checks for PQ/HLG like we do for sRGBish.
44 switch (-(int)tf.g) {
45 case PQish_TF: return PQish_TF;
46 case HLGish_TF: return HLGish_TF;
47 case HLGinvish_TF: return HLGinvish_TF;
48 }
49 return Bad_TF;
50 }
51
52 // Basic sanity checks for sRGBish transfer functions.
53 if (sk_float_isfinite(tf.a + tf.b + tf.c + tf.d + tf.e + tf.f + tf.g)
54 // a,c,d,g should be non-negative to make any sense.
55 && tf.a >= 0
56 && tf.c >= 0
57 && tf.d >= 0
58 && tf.g >= 0
59 // Raising a negative value to a fractional tf->g produces complex numbers.
60 && tf.a * tf.d + tf.b >= 0) {
61 return sRGBish_TF;
62 }
63
64 return Bad_TF;
65 }
66
is_almost_srgb(const skcms_TransferFunction & coeffs)67 static inline bool is_almost_srgb(const skcms_TransferFunction& coeffs) {
68 return transfer_fn_almost_equal(SkNamedTransferFn::kSRGB.a, coeffs.a) &&
69 transfer_fn_almost_equal(SkNamedTransferFn::kSRGB.b, coeffs.b) &&
70 transfer_fn_almost_equal(SkNamedTransferFn::kSRGB.c, coeffs.c) &&
71 transfer_fn_almost_equal(SkNamedTransferFn::kSRGB.d, coeffs.d) &&
72 transfer_fn_almost_equal(SkNamedTransferFn::kSRGB.e, coeffs.e) &&
73 transfer_fn_almost_equal(SkNamedTransferFn::kSRGB.f, coeffs.f) &&
74 transfer_fn_almost_equal(SkNamedTransferFn::kSRGB.g, coeffs.g);
75 }
76
is_almost_2dot2(const skcms_TransferFunction & coeffs)77 static inline bool is_almost_2dot2(const skcms_TransferFunction& coeffs) {
78 return transfer_fn_almost_equal(1.0f, coeffs.a) &&
79 transfer_fn_almost_equal(0.0f, coeffs.b) &&
80 transfer_fn_almost_equal(0.0f, coeffs.e) &&
81 transfer_fn_almost_equal(2.2f, coeffs.g) &&
82 coeffs.d <= 0.0f;
83 }
84
is_almost_linear(const skcms_TransferFunction & coeffs)85 static inline bool is_almost_linear(const skcms_TransferFunction& coeffs) {
86 // OutputVal = InputVal ^ 1.0f
87 const bool linearExp =
88 transfer_fn_almost_equal(1.0f, coeffs.a) &&
89 transfer_fn_almost_equal(0.0f, coeffs.b) &&
90 transfer_fn_almost_equal(0.0f, coeffs.e) &&
91 transfer_fn_almost_equal(1.0f, coeffs.g) &&
92 coeffs.d <= 0.0f;
93
94 // OutputVal = 1.0f * InputVal
95 const bool linearFn =
96 transfer_fn_almost_equal(1.0f, coeffs.c) &&
97 transfer_fn_almost_equal(0.0f, coeffs.f) &&
98 coeffs.d >= 1.0f;
99
100 return linearExp || linearFn;
101 }
102
103 // Return raw pointers to commonly used SkColorSpaces.
104 // No need to ref/unref these, but if you do, do it in pairs.
105 SkColorSpace* sk_srgb_singleton();
106 SkColorSpace* sk_srgb_linear_singleton();
107
108 #endif // SkColorSpacePriv_DEFINED
109