1 /*
2 * Copyright 2017 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 "include/effects/SkHighContrastFilter.h"
9
10 #include "include/core/SkColorFilter.h"
11 #include "include/core/SkRefCnt.h"
12 #include "include/core/SkTypes.h"
13
14 #ifdef SK_ENABLE_SKSL
15 #include "include/core/SkAlphaType.h"
16 #include "include/core/SkColorSpace.h"
17 #include "include/core/SkData.h"
18 #include "include/core/SkString.h"
19 #include "include/effects/SkRuntimeEffect.h"
20 #include "include/private/base/SkTPin.h"
21 #include "modules/skcms/skcms.h"
22 #include "src/core/SkColorFilterPriv.h"
23 #include "src/core/SkRuntimeEffectPriv.h"
24
25 #include <cfloat>
26
Make(const SkHighContrastConfig & config)27 sk_sp<SkColorFilter> SkHighContrastFilter::Make(const SkHighContrastConfig& config) {
28 if (!config.isValid()) {
29 return nullptr;
30 }
31
32 struct Uniforms { float grayscale, invertStyle, contrast; };
33
34 static constexpr char kHighContrastFilterCode[] =
35 "uniform half grayscale, invertStyle, contrast;"
36
37 // TODO(skia:13540): Investigate using $rgb_to_hsl from sksl_shared instead.
38 "half3 rgb_to_hsl(half3 c) {"
39 "half mx = max(max(c.r,c.g),c.b),"
40 "mn = min(min(c.r,c.g),c.b),"
41 "d = mx-mn,"
42 "invd = 1.0 / d,"
43 "g_lt_b = c.g < c.b ? 6.0 : 0.0;"
44
45 // We'd prefer to write these tests like `mx == c.r`, but on some GPUs max(x,y) is
46 // not always equal to either x or y. So we use long form, c.r >= c.g && c.r >= c.b.
47 "half h = (1/6.0) * (mx == mn ? 0.0 :"
48 /*mx==c.r*/ "c.r >= c.g && c.r >= c.b ? invd * (c.g - c.b) + g_lt_b :"
49 /*mx==c.g*/ "c.g >= c.b ? invd * (c.b - c.r) + 2.0"
50 /*mx==c.b*/ ": invd * (c.r - c.g) + 4.0);"
51 "half sum = mx+mn,"
52 "l = sum * 0.5,"
53 "s = mx == mn ? 0.0"
54 ": d / (l > 0.5 ? 2.0 - sum : sum);"
55 "return half3(h,s,l);"
56 "}"
57 "half4 main(half4 inColor) {"
58 "half4 c = inColor;" // linear unpremul RGBA in dst gamut
59 "if (grayscale == 1) {"
60 "c.rgb = dot(half3(0.2126, 0.7152, 0.0722), c.rgb).rrr;"
61 "}"
62 "if (invertStyle == 1) {" // brightness
63 "c.rgb = 1 - c.rgb;"
64 "} else if (invertStyle == 2) {" // lightness
65 "c.rgb = rgb_to_hsl(c.rgb);"
66 "c.b = 1 - c.b;"
67 "c.rgb = $hsl_to_rgb(c.rgb);"
68 "}"
69 "c.rgb = mix(half3(0.5), c.rgb, contrast);"
70 "return half4(saturate(c.rgb), c.a);"
71 "}";
72
73 static const SkRuntimeEffect* effect = SkMakeCachedRuntimeEffect(
74 SkRuntimeEffect::MakeForColorFilter,
75 SkString(kHighContrastFilterCode)
76 ).release();
77
78 SkASSERT(effect);
79
80 // A contrast setting of exactly +1 would divide by zero (1+c)/(1-c), so pull in to +1-ε.
81 // I'm not exactly sure why we've historically pinned -1 up to -1+ε, maybe just symmetry?
82 float c = SkTPin(config.fContrast,
83 -1.0f + FLT_EPSILON,
84 +1.0f - FLT_EPSILON);
85
86 Uniforms uniforms = {
87 config.fGrayscale ? 1.0f : 0.0f,
88 (float)config.fInvertStyle, // 0.0f for none, 1.0f for brightness, 2.0f for lightness
89 (1+c)/(1-c),
90 };
91
92 skcms_TransferFunction linear = SkNamedTransferFn::kLinear;
93 SkAlphaType unpremul = kUnpremul_SkAlphaType;
94 return SkColorFilterPriv::WithWorkingFormat(
95 effect->makeColorFilter(SkData::MakeWithCopy(&uniforms,sizeof(uniforms))),
96 &linear, nullptr/*use dst gamut*/, &unpremul);
97 }
98 #else // SK_ENABLE_SKSL
Make(const SkHighContrastConfig & config)99 sk_sp<SkColorFilter> SkHighContrastFilter::Make(const SkHighContrastConfig& config) {
100 // TODO(skia:12197)
101 return nullptr;
102 }
103 #endif
104
105