Introduce libshaders static library
This library is for exposing system-only shader implementations in SkSL.
Notably: libshaders depends on the vendor available libtonemap, but
libtonemap is vendor available as it is a single source of truth for
tonemap operations, whereas libshaders is not meant to be shared with
the vendor partition. Rather, the intent is to allow for sharing of SkSL
between librenderengine and libhwui.
Bug: 200309590
Ignore-AOSP-First: Introduces internal-only library
Test: builds
Change-Id: I611b79eb3addd15528f0cdb70e9f2f3d62473ec1
diff --git a/libs/shaders/shaders.cpp b/libs/shaders/shaders.cpp
new file mode 100644
index 0000000..ee2d4a4
--- /dev/null
+++ b/libs/shaders/shaders.cpp
@@ -0,0 +1,361 @@
+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <shaders/shaders.h>
+
+#include <tonemap/tonemap.h>
+
+#include <optional>
+
+#include <math/mat4.h>
+#include <system/graphics-base-v1.0.h>
+#include <ui/ColorSpace.h>
+
+namespace android::shaders {
+
+static aidl::android::hardware::graphics::common::Dataspace toAidlDataspace(
+ ui::Dataspace dataspace) {
+ return static_cast<aidl::android::hardware::graphics::common::Dataspace>(dataspace);
+}
+
+static void generateEOTF(ui::Dataspace dataspace, std::string& shader) {
+ switch (dataspace & HAL_DATASPACE_TRANSFER_MASK) {
+ case HAL_DATASPACE_TRANSFER_ST2084:
+ shader.append(R"(
+
+ float3 EOTF(float3 color) {
+ float m1 = (2610.0 / 4096.0) / 4.0;
+ float m2 = (2523.0 / 4096.0) * 128.0;
+ float c1 = (3424.0 / 4096.0);
+ float c2 = (2413.0 / 4096.0) * 32.0;
+ float c3 = (2392.0 / 4096.0) * 32.0;
+
+ float3 tmp = pow(clamp(color, 0.0, 1.0), 1.0 / float3(m2));
+ tmp = max(tmp - c1, 0.0) / (c2 - c3 * tmp);
+ return pow(tmp, 1.0 / float3(m1));
+ }
+ )");
+ break;
+ case HAL_DATASPACE_TRANSFER_HLG:
+ shader.append(R"(
+ float EOTF_channel(float channel) {
+ const float a = 0.17883277;
+ const float b = 0.28466892;
+ const float c = 0.55991073;
+ return channel <= 0.5 ? channel * channel / 3.0 :
+ (exp((channel - c) / a) + b) / 12.0;
+ }
+
+ float3 EOTF(float3 color) {
+ return float3(EOTF_channel(color.r), EOTF_channel(color.g),
+ EOTF_channel(color.b));
+ }
+ )");
+ break;
+ case HAL_DATASPACE_TRANSFER_LINEAR:
+ shader.append(R"(
+ float3 EOTF(float3 color) {
+ return color;
+ }
+ )");
+ break;
+ case HAL_DATASPACE_TRANSFER_SRGB:
+ default:
+ shader.append(R"(
+
+ float EOTF_sRGB(float srgb) {
+ return srgb <= 0.04045 ? srgb / 12.92 : pow((srgb + 0.055) / 1.055, 2.4);
+ }
+
+ float3 EOTF_sRGB(float3 srgb) {
+ return float3(EOTF_sRGB(srgb.r), EOTF_sRGB(srgb.g), EOTF_sRGB(srgb.b));
+ }
+
+ float3 EOTF(float3 srgb) {
+ return sign(srgb.rgb) * EOTF_sRGB(abs(srgb.rgb));
+ }
+ )");
+ break;
+ }
+}
+
+static void generateXYZTransforms(std::string& shader) {
+ shader.append(R"(
+ uniform float4x4 in_rgbToXyz;
+ uniform float4x4 in_xyzToRgb;
+ float3 ToXYZ(float3 rgb) {
+ return (in_rgbToXyz * float4(rgb, 1.0)).rgb;
+ }
+
+ float3 ToRGB(float3 xyz) {
+ return clamp((in_xyzToRgb * float4(xyz, 1.0)).rgb, 0.0, 1.0);
+ }
+ )");
+}
+
+// Conversion from relative light to absolute light (maps from [0, 1] to [0, maxNits])
+static void generateLuminanceScalesForOOTF(ui::Dataspace inputDataspace,
+ ui::Dataspace outputDataspace, std::string& shader) {
+ switch (inputDataspace & HAL_DATASPACE_TRANSFER_MASK) {
+ case HAL_DATASPACE_TRANSFER_ST2084:
+ shader.append(R"(
+ float3 ScaleLuminance(float3 xyz) {
+ return xyz * 10000.0;
+ }
+ )");
+ break;
+ case HAL_DATASPACE_TRANSFER_HLG:
+ shader.append(R"(
+ float3 ScaleLuminance(float3 xyz) {
+ return xyz * 1000.0 * pow(xyz.y, 0.2);
+ }
+ )");
+ break;
+ default:
+ switch (outputDataspace & HAL_DATASPACE_TRANSFER_MASK) {
+ case HAL_DATASPACE_TRANSFER_ST2084:
+ case HAL_DATASPACE_TRANSFER_HLG:
+ // SDR -> HDR tonemap
+ shader.append(R"(
+ float3 ScaleLuminance(float3 xyz) {
+ return xyz * in_libtonemap_inputMaxLuminance;
+ }
+ )");
+ break;
+ default:
+ // Input and output are both SDR, so no tone-mapping is expected so
+ // no-op the luminance normalization.
+ shader.append(R"(
+ float3 ScaleLuminance(float3 xyz) {
+ return xyz * in_libtonemap_displayMaxLuminance;
+ }
+ )");
+ break;
+ }
+ }
+}
+
+// Normalizes from absolute light back to relative light (maps from [0, maxNits] back to [0, 1])
+static void generateLuminanceNormalizationForOOTF(ui::Dataspace outputDataspace,
+ std::string& shader) {
+ switch (outputDataspace & HAL_DATASPACE_TRANSFER_MASK) {
+ case HAL_DATASPACE_TRANSFER_ST2084:
+ shader.append(R"(
+ float3 NormalizeLuminance(float3 xyz) {
+ return xyz / 10000.0;
+ }
+ )");
+ break;
+ case HAL_DATASPACE_TRANSFER_HLG:
+ shader.append(R"(
+ float3 NormalizeLuminance(float3 xyz) {
+ return xyz / 1000.0 * pow(xyz.y / 1000.0, -0.2 / 1.2);
+ }
+ )");
+ break;
+ default:
+ shader.append(R"(
+ float3 NormalizeLuminance(float3 xyz) {
+ return xyz / in_libtonemap_displayMaxLuminance;
+ }
+ )");
+ break;
+ }
+}
+
+static void generateOOTF(ui::Dataspace inputDataspace, ui::Dataspace outputDataspace,
+ std::string& shader) {
+ shader.append(tonemap::getToneMapper()
+ ->generateTonemapGainShaderSkSL(toAidlDataspace(inputDataspace),
+ toAidlDataspace(outputDataspace))
+ .c_str());
+
+ generateLuminanceScalesForOOTF(inputDataspace, outputDataspace, shader);
+ generateLuminanceNormalizationForOOTF(outputDataspace, shader);
+
+ shader.append(R"(
+ float3 OOTF(float3 linearRGB, float3 xyz) {
+ float3 scaledLinearRGB = ScaleLuminance(linearRGB);
+ float3 scaledXYZ = ScaleLuminance(xyz);
+
+ float gain = libtonemap_LookupTonemapGain(scaledLinearRGB, scaledXYZ);
+
+ return NormalizeLuminance(scaledXYZ * gain);
+ }
+ )");
+}
+
+static void generateOETF(ui::Dataspace dataspace, std::string& shader) {
+ switch (dataspace & HAL_DATASPACE_TRANSFER_MASK) {
+ case HAL_DATASPACE_TRANSFER_ST2084:
+ shader.append(R"(
+
+ float3 OETF(float3 xyz) {
+ float m1 = (2610.0 / 4096.0) / 4.0;
+ float m2 = (2523.0 / 4096.0) * 128.0;
+ float c1 = (3424.0 / 4096.0);
+ float c2 = (2413.0 / 4096.0) * 32.0;
+ float c3 = (2392.0 / 4096.0) * 32.0;
+
+ float3 tmp = pow(xyz, float3(m1));
+ tmp = (c1 + c2 * tmp) / (1.0 + c3 * tmp);
+ return pow(tmp, float3(m2));
+ }
+ )");
+ break;
+ case HAL_DATASPACE_TRANSFER_HLG:
+ shader.append(R"(
+ float OETF_channel(float channel) {
+ const float a = 0.17883277;
+ const float b = 0.28466892;
+ const float c = 0.55991073;
+ return channel <= 1.0 / 12.0 ? sqrt(3.0 * channel) :
+ a * log(12.0 * channel - b) + c;
+ }
+
+ float3 OETF(float3 linear) {
+ return float3(OETF_channel(linear.r), OETF_channel(linear.g),
+ OETF_channel(linear.b));
+ }
+ )");
+ break;
+ case HAL_DATASPACE_TRANSFER_LINEAR:
+ shader.append(R"(
+ float3 OETF(float3 linear) {
+ return linear;
+ }
+ )");
+ break;
+ case HAL_DATASPACE_TRANSFER_SRGB:
+ default:
+ shader.append(R"(
+ float OETF_sRGB(float linear) {
+ return linear <= 0.0031308 ?
+ linear * 12.92 : (pow(linear, 1.0 / 2.4) * 1.055) - 0.055;
+ }
+
+ float3 OETF_sRGB(float3 linear) {
+ return float3(OETF_sRGB(linear.r), OETF_sRGB(linear.g), OETF_sRGB(linear.b));
+ }
+
+ float3 OETF(float3 linear) {
+ return sign(linear.rgb) * OETF_sRGB(abs(linear.rgb));
+ }
+ )");
+ break;
+ }
+}
+
+static void generateEffectiveOOTF(bool undoPremultipliedAlpha, std::string& shader) {
+ shader.append(R"(
+ uniform shader child;
+ half4 main(float2 xy) {
+ float4 c = float4(child.eval(xy));
+ )");
+ if (undoPremultipliedAlpha) {
+ shader.append(R"(
+ c.rgb = c.rgb / (c.a + 0.0019);
+ )");
+ }
+ shader.append(R"(
+ float3 linearRGB = EOTF(c.rgb);
+ float3 xyz = ToXYZ(linearRGB);
+ c.rgb = OETF(ToRGB(OOTF(linearRGB, xyz)));
+ )");
+ if (undoPremultipliedAlpha) {
+ shader.append(R"(
+ c.rgb = c.rgb * (c.a + 0.0019);
+ )");
+ }
+ shader.append(R"(
+ return c;
+ }
+ )");
+}
+static ColorSpace toColorSpace(ui::Dataspace dataspace) {
+ switch (dataspace & HAL_DATASPACE_STANDARD_MASK) {
+ case HAL_DATASPACE_STANDARD_BT709:
+ return ColorSpace::sRGB();
+ break;
+ case HAL_DATASPACE_STANDARD_DCI_P3:
+ return ColorSpace::DisplayP3();
+ break;
+ case HAL_DATASPACE_STANDARD_BT2020:
+ return ColorSpace::BT2020();
+ break;
+ default:
+ return ColorSpace::sRGB();
+ break;
+ }
+}
+
+std::string buildLinearEffectSkSL(const LinearEffect& linearEffect) {
+ std::string shaderString;
+ generateEOTF(linearEffect.fakeInputDataspace == ui::Dataspace::UNKNOWN
+ ? linearEffect.inputDataspace
+ : linearEffect.fakeInputDataspace,
+ shaderString);
+ generateXYZTransforms(shaderString);
+ generateOOTF(linearEffect.inputDataspace, linearEffect.outputDataspace, shaderString);
+ generateOETF(linearEffect.outputDataspace, shaderString);
+ generateEffectiveOOTF(linearEffect.undoPremultipliedAlpha, shaderString);
+ return shaderString;
+}
+
+template <typename T, std::enable_if_t<std::is_trivially_copyable<T>::value, bool> = true>
+std::vector<uint8_t> buildUniformValue(T value) {
+ std::vector<uint8_t> result;
+ result.resize(sizeof(value));
+ std::memcpy(result.data(), &value, sizeof(value));
+ return result;
+}
+
+// Generates a list of uniforms to set on the LinearEffect shader above.
+std::vector<tonemap::ShaderUniform> buildLinearEffectUniforms(const LinearEffect& linearEffect,
+ const mat4& colorTransform,
+ float maxDisplayLuminance,
+ float maxLuminance) {
+ std::vector<tonemap::ShaderUniform> uniforms;
+ if (linearEffect.inputDataspace == linearEffect.outputDataspace) {
+ uniforms.push_back({.name = "in_rgbToXyz", .value = buildUniformValue<mat4>(mat4())});
+ uniforms.push_back(
+ {.name = "in_xyzToRgb", .value = buildUniformValue<mat4>(colorTransform)});
+ } else {
+ ColorSpace inputColorSpace = toColorSpace(linearEffect.inputDataspace);
+ ColorSpace outputColorSpace = toColorSpace(linearEffect.outputDataspace);
+ uniforms.push_back({.name = "in_rgbToXyz",
+ .value = buildUniformValue<mat4>(mat4(inputColorSpace.getRGBtoXYZ()))});
+ uniforms.push_back({.name = "in_xyzToRgb",
+ .value = buildUniformValue<mat4>(
+ colorTransform * mat4(outputColorSpace.getXYZtoRGB()))});
+ }
+
+ tonemap::Metadata metadata{.displayMaxLuminance = maxDisplayLuminance,
+ // If the input luminance is unknown, use display luminance (aka,
+ // no-op any luminance changes)
+ // This will be the case for eg screenshots in addition to
+ // uncalibrated displays
+ .contentMaxLuminance =
+ maxLuminance > 0 ? maxLuminance : maxDisplayLuminance};
+
+ for (const auto uniform : tonemap::getToneMapper()->generateShaderSkSLUniforms(metadata)) {
+ uniforms.push_back(uniform);
+ }
+
+ return uniforms;
+}
+
+} // namespace android::shaders
\ No newline at end of file