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ycbcr_709_v2.cpp
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ycbcr_709_v2.cpp
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// SPDX-FileCopyrightText: 2022 Amyspark <[email protected]>
// SPDX-License-Identifier: BSD-3-Clause
#include <lcms2.h>
#include <array>
#include <iostream>
#include "version.h"
#define RESOLUTION 24
// Source: Tooms (2015), table 11.1, p.192
constexpr cmsCIExyY d65 = {0.3127, 0.3290, 1.0};
#if !defined BT1886
// Inverse OETF curve
//
// Source: basic algebra on ITU-R BT.709-6, ss. 1.2
constexpr std::array<cmsFloat64Number, 5> rec709ParametersInv = {1.0 / 0.45, 1.0 / 1.099, 0.099 / 1.099, 1.0 / 4.5, 0.081};
// OETF curve
//
// Source: ITU-R BT.709-6, ss. 1.2
const std::array<cmsFloat64Number, 7> rec709Parameters = {0.45, 1.099, 0, 4.5, 0.018, -0.099, 0};
#endif
void log(cmsContext ctx, unsigned int errorCode, const char *msg)
{
std::cerr << "context " << ctx << " error: " << errorCode << " (" << msg << ")" << std::endl;
}
cmsInt32Number sample(const cmsUInt16Number In[], cmsUInt16Number Out[], void *cargo)
{
cmsPipelineEval16(In, Out, reinterpret_cast<cmsPipeline *>(cargo));
return TRUE;
}
// From the V4 profile above EXTRACT:
// - cmsSigMediaWhitePointTag
// - any of the cmsSigRedTRCTag, cmsSigGreenTRCTag, cmsSigBlueTRCTag
// - cmsSigChromaticAdaptationTag
// and use with the YCbCr profile
cmsHPROFILE createBaseRec709Profile(cmsContext ctx)
{
// Elle Stone's prequantized sRGB primaries
// Match: Tooms (2015), table 19.1
const cmsCIExyYTRIPLE sRGBPrimariesPreQuantized = {{0.639998686, 0.330010138, 1.0}, {0.300003784, 0.600003357, 1.0}, {0.150002046, 0.059997204, 1.0}};
#if defined BT1886
auto toneCurveInv = cmsBuildGamma(ctx, 2.4);
#else
auto toneCurveInv = cmsBuildParametricToneCurve(ctx, 4, rec709ParametersInv.data());
#endif
const std::array<cmsToneCurve *, T_CHANNELS(TYPE_RGB_16)> curves = {toneCurveInv, toneCurveInv, toneCurveInv};
return cmsCreateRGBProfileTHR(ctx, &d65, &sRGBPrimariesPreQuantized, curves.data());
}
void setupMetadata(cmsContext ctx, cmsHPROFILE profile)
{
std::string version{COMMIT};
auto copyright = cmsMLUalloc(ctx, 1);
cmsMLUsetASCII(copyright,
"en",
"US",
"(C) 2022 Amyspark <[email protected]>. This work is licensed under the Creative Commons Attribution-ShareAlike 4.0 International License. To "
"view a copy of this license, visit <http://creativecommons.org/licenses/by-sa/4.0/>.");
cmsWriteTag(profile, cmsSigCopyrightTag, copyright);
auto description = cmsMLUalloc(ctx, 1);
#if defined BT1886
cmsMLUsetASCII(description, "en", "US", "ITU-R BT.709-6 + BT.1886 YCbCr ICC V2 profile");
#else
cmsMLUsetASCII(description, "en", "US", "ITU-R BT.709-6 YCbCr ICC V2 profile");
#endif
cmsWriteTag(profile, cmsSigProfileDescriptionTag, description);
auto MfgDesc = cmsMLUalloc(ctx, 1);
cmsMLUsetASCII(MfgDesc, "en", "US", "Amyspark");
cmsWriteTag(profile, cmsSigDeviceMfgDescTag, MfgDesc);
auto ModelDesc = cmsMLUalloc(ctx, 1);
cmsMLUsetASCII(ModelDesc, "en", "US", version.c_str());
cmsWriteTag(profile, cmsSigDeviceModelDescTag, ModelDesc);
cmsSetHeaderManufacturer(profile, 0x494E544C);
cmsSetHeaderModel(profile, 0x494E544C);
}
int main()
{
cmsSetLogErrorHandlerTHR(nullptr, log);
auto ctx = cmsCreateContext(nullptr, nullptr);
auto baseProfile = createBaseRec709Profile(ctx);
// cmsSaveProfileToFile(baseProfile, "srgb.icc");
auto yCbrProfile = cmsCreateLab2Profile(&d65);
setupMetadata(ctx, yCbrProfile);
// Strict transformation between YCbCr and XYZ
#if defined BT1886
cmsSetDeviceClass(yCbrProfile, cmsSigDisplayClass);
#else
cmsSetDeviceClass(yCbrProfile, cmsSigColorSpaceClass);
#endif
cmsSetColorSpace(yCbrProfile, cmsSigYCbCrData);
cmsSetPCS(yCbrProfile, cmsSigXYZData);
cmsSetHeaderRenderingIntent(yCbrProfile, INTENT_PERCEPTUAL);
// The YCbCr -> XYZ conversion goes as follows:
auto yCbrPipeline = cmsPipelineAlloc(ctx, T_CHANNELS(TYPE_YCbCr_16), T_CHANNELS(TYPE_XYZ_16));
// 0. Dummy curves for the "gamma"-corrected YCbCr.
auto pipeline1_M = cmsStageAllocToneCurves(ctx, T_CHANNELS(TYPE_YCbCr_16), nullptr);
// 1. Chrominance channels are [-0.5, 0.5]. Adjust.
// The offset is pre-applied before the transform.
const std::array<double, T_CHANNELS(TYPE_YCbCr_16) * T_CHANNELS(TYPE_YCbCr_16)> identity = {{1, 0, 0, 0, 1, 0, 0, 0, 1}};
const std::array<double, T_CHANNELS(TYPE_YCbCr_16)> offset_ycbcr_to_rgb = {0, -0.5, -0.5};
auto yCbrOffset = cmsStageAllocMatrix(ctx, T_CHANNELS(TYPE_YCbCr_16), T_CHANNELS(TYPE_YCbCr_16), identity.data(), offset_ycbcr_to_rgb.data());
// 2. YCbCr -> normalized R'G'B. Source: Wolfram Alpha, inverted matrix.
const std::array<double, T_CHANNELS(TYPE_YCbCr_16) * T_CHANNELS(TYPE_RGB_16)> ycbcr_to_rgb = {
{1, 0, 1.5748, 1, -0.187324, -0.468124, 1, 1.8556, -4.60823e-17}};
auto yCbrMatrix = cmsStageAllocMatrix(ctx, T_CHANNELS(TYPE_YCbCr_16), T_CHANNELS(TYPE_RGB_16), ycbcr_to_rgb.data(), nullptr);
auto trc = reinterpret_cast<cmsToneCurve *>(cmsReadTag(baseProfile, cmsSigRedTRCTag));
#if defined BT1886
// 2. Normalized R'G'B -> linear RGB. Source: ITU-R BT.1886
const std::array<cmsToneCurve *, T_CHANNELS(TYPE_RGB_16)> gamma = {trc, trc, trc};
#else
// 2. Normalized R'G'B -> linear RGB. Source: ITU-R BT.709-6, ss. 1.2
// Workaround littleCMS going haywire on type 5 parametric curves
auto trcClut = [ctx, trc]() {
std::array<cmsFloat32Number, 1024> test{};
for (auto i = 0; i < 1024; i++) {
cmsFloat32Number x = 1.0f / 1024.0f * (cmsFloat32Number)i;
test[i] = cmsEvalToneCurveFloat(trc, x);
}
return cmsBuildTabulatedToneCurveFloat(ctx, test.size(), test.data());
}();
const std::array<cmsToneCurve *, T_CHANNELS(TYPE_RGB_16)> gamma = {trcClut, trcClut, trcClut};
#endif
auto pipeline1_B = cmsStageAllocToneCurves(ctx, T_CHANNELS(TYPE_RGB_16), gamma.data());
// 3. Linear RGB -> XYZ.
// Source: <https://photosauce.net/blog/post/making-a-minimal-srgb-icc-profile-part-3-choose-your-colors-carefully>
// NOTE: these must be computed under D65!!!
const std::array<double, T_CHANNELS(TYPE_RGB_16) * T_CHANNELS(TYPE_XYZ_16)> rgb_to_xyz = {
{0.4124, 0.3576, 0.1805, 0.2126, 0.7152, 0.0722, 0.0193, 0.1192, 0.9505}};
auto pipeline1_C = cmsStageAllocMatrix(ctx, T_CHANNELS(TYPE_RGB_16), T_CHANNELS(TYPE_XYZ_16), rgb_to_xyz.data(), nullptr);
// Assemble the YCbCr -> XYZ pipeline.
cmsPipelineInsertStage(yCbrPipeline, cmsAT_END, yCbrOffset);
cmsPipelineInsertStage(yCbrPipeline, cmsAT_END, yCbrMatrix);
cmsPipelineInsertStage(yCbrPipeline, cmsAT_END, pipeline1_B); // M = OETF
cmsPipelineInsertStage(yCbrPipeline, cmsAT_END, pipeline1_C); // Matrix = RGB -> XYZ
auto lut1 = cmsStageAllocCLut16bit(ctx, RESOLUTION, T_CHANNELS(TYPE_YCbCr_16), T_CHANNELS(TYPE_XYZ_16), nullptr);
cmsStageSampleCLut16bit(lut1, &sample, yCbrPipeline, 0);
// This LUT is then saved to the profile
auto p = cmsPipelineAlloc(ctx, T_CHANNELS(TYPE_YCbCr_16), T_CHANNELS(TYPE_XYZ_16));
cmsPipelineInsertStage(p, cmsAT_END, pipeline1_M); // A = dummy curves
// The CLUT is needed because AtoB0 in v2 can only pack a CLUT.
cmsPipelineInsertStage(p, cmsAT_END, lut1); // CLUT = YCbr -> XYZ
cmsPipelineInsertStage(p, cmsAT_END, cmsStageDup(pipeline1_M)); // B = dummy curves
cmsWriteTag(yCbrProfile, cmsSigAToB0Tag, p);
// The XYZ -> YCbCr conversion goes as follows:
auto yCbrPipeline2 = cmsPipelineAlloc(ctx, T_CHANNELS(TYPE_XYZ_16), T_CHANNELS(TYPE_YCbCr_16));
// 0. Dummy curves for the gamma-uncorrected YCbCr.
auto pipeline2_M = cmsStageAllocToneCurves(ctx, T_CHANNELS(TYPE_RGB_16), nullptr);
// 1. XYZ -> Linear RGB.
// Source: <https://photosauce.net/blog/post/making-a-minimal-srgb-icc-profile-part-3-choose-your-colors-carefully>
const std::array<double, T_CHANNELS(TYPE_XYZ_16) * T_CHANNELS(TYPE_RGB_16)> xyz_to_rgb = {
{3.2406, -1.5372, -0.4986, -0.9689, 1.8758, 0.0415, 0.0557, -0.2040, 1.0570}};
auto pipeline2_C = cmsStageAllocMatrix(ctx, T_CHANNELS(TYPE_XYZ_16), T_CHANNELS(TYPE_RGB_16), xyz_to_rgb.data(), nullptr);
#if defined BT1886
// 2. Linear RGB -> Normalized R'G'B. Source: ITU-R BT.1886
auto trcI = cmsBuildGamma(ctx, 1.0 / 2.4);
const std::array<cmsToneCurve *, T_CHANNELS(TYPE_RGB_16)> gamma_i = {trcI, trcI, trcI};
#else
// 2. Linear RGB -> Normalized R'G'B. Source: ITU-R BT.709-6, ss. 3.1
// Workaround littleCMS going haywire on type 5 parametric curves
auto trcI = cmsBuildParametricToneCurve(ctx, 5, rec709Parameters.data());
auto trcIClut = [ctx, trcI]() {
std::array<cmsFloat32Number, 1024> test{};
for (auto i = 0; i < 1024; i++) {
cmsFloat32Number x = 1.0f / 1024.0f * (cmsFloat32Number)i;
test[i] = cmsEvalToneCurveFloat(trcI, x);
}
return cmsBuildTabulatedToneCurveFloat(ctx, test.size(), test.data());
}();
const std::array<cmsToneCurve *, T_CHANNELS(TYPE_RGB_16)> gamma_i = {trcIClut, trcIClut, trcIClut};
#endif
auto pipeline2_B = cmsStageAllocToneCurves(ctx, T_CHANNELS(TYPE_RGB_16), gamma_i.data());
// 3. Normalized R'G'B -> YCbCr.
// Source: ITU-R BT.709-6, ss. 3.3.
// XXX: nudge these with xicclu?
const std::array<double, T_CHANNELS(TYPE_RGB_16) * T_CHANNELS(TYPE_YCbCr_16)> rgb_to_ycbcr = {
{0.2126, 0.7152, 0.0722, -0.2126 / 1.8556, -0.7152 / 1.8556, 0.9278 / 1.8556, 0.7874 / 1.5748, -0.7152 / 1.5748, -0.0722 / 1.5748}};
// 4. Chrominance channels are [-0.5, 0.5]. Adjust.
// The offset is applied after the transform, so no additional matrix is
// needed.
const std::array<double, T_CHANNELS(TYPE_YCbCr_16)> offset_i = {0, 0.5, 0.5};
auto pipeline2_Matrix = cmsStageAllocMatrix(ctx, T_CHANNELS(TYPE_RGB_16), T_CHANNELS(TYPE_YCbCr_16), rgb_to_ycbcr.data(), offset_i.data());
cmsPipelineInsertStage(yCbrPipeline2, cmsAT_END, pipeline2_C); // Matrix = XYZ -> RGB
cmsPipelineInsertStage(yCbrPipeline2, cmsAT_END, pipeline2_B); // M = OETF^-1
cmsPipelineInsertStage(yCbrPipeline2, cmsAT_END, pipeline2_Matrix);
auto lut2 = cmsStageAllocCLut16bit(ctx, RESOLUTION, T_CHANNELS(TYPE_XYZ_16), T_CHANNELS(TYPE_YCbCr_16), nullptr);
cmsStageSampleCLut16bit(lut2, &sample, yCbrPipeline2, 0);
auto p2 = cmsPipelineAlloc(ctx, T_CHANNELS(TYPE_XYZ_16), T_CHANNELS(TYPE_YCbCr_16));
cmsPipelineInsertStage(p2, cmsAT_END, pipeline2_M); // B = dummy
cmsPipelineInsertStage(p2, cmsAT_END, lut2); // CLUT = R'G'B' -> YCbr
cmsPipelineInsertStage(p2, cmsAT_END, cmsStageDup(pipeline2_M)); // A = dummy
cmsWriteTag(yCbrProfile, cmsSigBToA0Tag, p2);
// Bradford transform from D65 (BT.709-6) to D50 (ICC 4.3)
// Source: Elle Stone's well behaved sRGB profile
// Thanks to Doug Walker from ILM for pointing it out.
auto bradford = cmsReadTag(baseProfile, cmsSigChromaticAdaptationTag);
cmsWriteTag(yCbrProfile, cmsSigChromaticAdaptationTag, bradford);
if (!cmsMD5computeID(yCbrProfile)) {
std::cerr << "Failed MD5 computation" << std::endl;
return -1;
}
#if defined BT1886
const std::string profileName{"bt709-6_bt1886_ycbcr_v2.icc"};
#else
const std::string profileName{"bt709-6_ycbcr_v2.icc"};
#endif
if (!cmsSaveProfileToFile(yCbrProfile, profileName.c_str())) {
std::cerr << "CANNOT WRITE PROFILE" << std::endl;
return -2;
}
}