1 /*
2 * Copyright 2024 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "GainmapFactory.h"
18
19 #include <log/log.h>
20
21 namespace android {
22 namespace renderengine {
23 namespace skia {
24 namespace {
25
makeEffect(const SkString & sksl)26 sk_sp<SkRuntimeEffect> makeEffect(const SkString& sksl) {
27 auto [effect, error] = SkRuntimeEffect::MakeForShader(sksl);
28 LOG_ALWAYS_FATAL_IF(!effect, "RuntimeShader error: %s", error.c_str());
29 return effect;
30 }
31
32 // Please refer to https://developer.android.com/media/platform/hdr-image-format#gain_map-generation
33 static const SkString kGainmapShader = SkString(R"(
34 uniform shader sdr;
35 uniform shader hdr;
36 uniform float mapMaxLog2;
37
38 const float mapMinLog2 = 0.0;
39 const float mapGamma = 1.0;
40 const float offsetSdr = 0.015625;
41 const float offsetHdr = 0.015625;
42
43 float luminance(vec3 linearColor) {
44 return 0.2126 * linearColor.r + 0.7152 * linearColor.g + 0.0722 * linearColor.b;
45 }
46
47 vec4 main(vec2 xy) {
48 float sdrY = luminance(toLinearSrgb(sdr.eval(xy).rgb));
49 float hdrY = luminance(toLinearSrgb(hdr.eval(xy).rgb));
50 float pixelGain = (hdrY + offsetHdr) / (sdrY + offsetSdr);
51 float logRecovery = (log2(pixelGain) - mapMinLog2) / (mapMaxLog2 - mapMinLog2);
52 return vec4(pow(clamp(logRecovery, 0.0, 1.0), mapGamma));
53 }
54 )");
55 } // namespace
56
57 const float INTERPOLATION_STRENGTH_VALUE = 0.7f;
58
GainmapFactory()59 GainmapFactory::GainmapFactory() : mEffect(makeEffect(kGainmapShader)) {}
60
createSkShader(const sk_sp<SkShader> & sdr,const sk_sp<SkShader> & hdr,float hdrSdrRatio)61 sk_sp<SkShader> GainmapFactory::createSkShader(const sk_sp<SkShader>& sdr,
62 const sk_sp<SkShader>& hdr, float hdrSdrRatio) {
63 SkRuntimeShaderBuilder shaderBuilder(mEffect);
64 shaderBuilder.child("sdr") = sdr;
65 shaderBuilder.child("hdr") = hdr;
66 shaderBuilder.uniform("mapMaxLog2") = std::log2(hdrSdrRatio);
67 return shaderBuilder.makeShader();
68 }
69
70 } // namespace skia
71 } // namespace renderengine
72 } // namespace android
73