Add BT1886 view EOTF (#928)

* Add BT1886 view EOTF --------- Co-authored-by: cedric <cedric.paille@gmail.com> Co-authored-by: Frédéric Devernay <devernay@users.noreply.github.com>
NatronGitHub · Nov 28, 2023 · e81c3f3 · e81c3f3
1 parent 2acaa84
commit e81c3f3
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Showing 10 changed files with 50 additions and 7 deletions.
diff --git a/Engine/ImageConvert.cpp b/Engine/ImageConvert.cpp
@@ -115,6 +115,9 @@ lutFromColorspace(ViewerColorSpaceEnum cs)
     case eViewerColorSpaceRec709:
         lut = Color::LutManager::Rec709Lut();
         break;
+    case eViewerColorSpaceBT1886:
+        lut = Color::LutManager::BT1886Lut();
+        break;
     case eViewerColorSpaceLinear:
     default:
         lut = 0;

diff --git a/Engine/Lut.cpp b/Engine/Lut.cpp
@@ -1293,6 +1293,12 @@ LutManager::sRGBLut()
     return LutManager::m_instance.getLut("sRGB", from_func_srgb, to_func_srgb);
 }
 
+const Lut*
+LutManager::BT1886Lut()
+{
+    return LutManager::m_instance.getLut("BT1886", from_func_bt1886, to_func_bt1886);
+}
+
 // Rec.709 and Rec.2020 share the same transfer function (and illuminant), except that
 // Rec.2020 is more precise.
 // https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.2020-0-201208-S!!PDF-E.pdf

diff --git a/Engine/Lut.h b/Engine/Lut.h
@@ -89,6 +89,7 @@ class LutManager
     ///buit-ins color-spaces
     static const Lut* sRGBLut();
     static const Lut* Rec709Lut();
+    static const Lut* BT1886Lut();
     static const Lut* CineonLut();
     static const Lut* Gamma1_8Lut();
     static const Lut* Gamma2_2Lut();
@@ -496,6 +497,18 @@ to_func_srgb(float v)
     }
 }
 
+inline float
+from_func_bt1886(float v)
+{
+    return std::pow(v, 2.4);
+}
+
+inline float
+to_func_bt1886(float v)
+{
+    return std::pow(v, 1.0/2.4);
+}
+
 // r,g,b values are from 0 to 1
 // h = [0,NATRON_COLOR_HUE_CIRCLE], s = [0,1], v = [0,1]
 //		if s == 0, then h = 0 (undefined)

diff --git a/Engine/Project.cpp b/Engine/Project.cpp
@@ -1001,6 +1001,7 @@ Project::initializeKnobs()
     colorSpaces.push_back(ChoiceOption("Linear","",""));
     colorSpaces.push_back(ChoiceOption("sRGB","",""));
     colorSpaces.push_back(ChoiceOption("Rec.709","",""));
+    colorSpaces.push_back(ChoiceOption("BT1886","",""));
 
     _imp->colorSpace8u = AppManager::createKnob<KnobChoice>( this, tr("8-Bit LUT") );
     _imp->colorSpace8u->setName("defaultColorSpace8u");

diff --git a/Engine/ViewerInstance.cpp b/Engine/ViewerInstance.cpp
@@ -140,6 +140,9 @@ ViewerInstance::lutFromColorspace(ViewerColorSpaceEnum cs)
     case eViewerColorSpaceRec709:
         lut = Color::LutManager::Rec709Lut();
         break;
+    case eViewerColorSpaceBT1886:
+        lut = Color::LutManager::BT1886Lut();
+        break;
     case eViewerColorSpaceLinear:
     default:
         lut = 0;

diff --git a/Global/Enums.h b/Global/Enums.h
@@ -441,7 +441,8 @@ enum ViewerColorSpaceEnum
 {
     eViewerColorSpaceSRGB = 0,
     eViewerColorSpaceLinear,
-    eViewerColorSpaceRec709
+    eViewerColorSpaceRec709,
+    eViewerColorSpaceBT1886
 };
 
 enum ImageBitDepthEnum

diff --git a/Gui/Shaders.cpp b/Gui/Shaders.cpp
@@ -42,21 +42,31 @@ const char* fragRGB =
     "float linear_to_rec709(float c) {"
     "    return (c<0.018) ? (4.500*c) : (1.099*pow(c,0.45) - 0.099);\n"
     "}\n"
-    "void main(){\n"
+    "float linear_to_bt1886(float c) {"
+    "    return pow(c,1.0/2.4);\n"
+    "}\n"
+    "void main() {\n"
     "    vec4 color_tmp = texture2D(Tex,gl_TexCoord[0].st);\n"
     "    color_tmp.rgb = (color_tmp.rgb * gain) + offset;\n"
-    "    if(lut == 0){ // srgb\n"
+    "    if (lut == 0) { // srgb\n"
 // << TO SRGB
     "       color_tmp.r = linear_to_srgb(color_tmp.r);\n"
     "       color_tmp.g = linear_to_srgb(color_tmp.g);\n"
     "       color_tmp.b = linear_to_srgb(color_tmp.b);\n"
 // << END TO SRGB
-    "   }\n"
-    "   else if (lut == 2){ // Rec 709\n" // << TO REC 709
+    "   } else if (lut == 2) { // Rec 709\n"
+// << TO REC 709
     "       color_tmp.r = linear_to_rec709(color_tmp.r);\n"
     "       color_tmp.g = linear_to_rec709(color_tmp.g);\n"
     "       color_tmp.b = linear_to_rec709(color_tmp.b);\n"
-    "   }\n" // << END TO REC 709
+// << END TO REC 709
+    "   } else if (lut == 3) { // BT1886\n"
+// << TO BT1886
+    "       color_tmp.r = linear_to_bt1886(color_tmp.r);\n"
+    "       color_tmp.g = linear_to_bt1886(color_tmp.g);\n"
+    "       color_tmp.b = linear_to_bt1886(color_tmp.b);\n"
+// << END TO BT1886
+    "   }\n"
     "   if (gamma <= 0.) {\n"
     "       color_tmp.r = (color_tmp.r >= 1.) ? 1. : 0.;\n"
     "       color_tmp.g = (color_tmp.g >= 1.) ? 1. : 0.;\n"

diff --git a/Gui/ViewerTab.cpp b/Gui/ViewerTab.cpp
@@ -528,6 +528,7 @@ ViewerTab::ViewerTab(const std::list<NodeGuiPtr> & existingNodesContext,
     _imp->viewerColorSpace->addItem( QString::fromUtf8("Linear(None)") );
     _imp->viewerColorSpace->addItem( QString::fromUtf8("sRGB") );
     _imp->viewerColorSpace->addItem( QString::fromUtf8("Rec.709") );
+    _imp->viewerColorSpace->addItem( QString::fromUtf8("BT1886") );
     _imp->viewerColorSpace->setCurrentIndex(1);
 
     QPixmap pixCheckerboardEnabled, pixCheckerboardDisabld;

diff --git a/Gui/ViewerTab10.cpp b/Gui/ViewerTab10.cpp
@@ -76,6 +76,8 @@ ViewerTab::onColorSpaceComboBoxChanged(int v)
         colorspace = eViewerColorSpaceSRGB;
     } else if (v == 2) {
         colorspace = eViewerColorSpaceRec709;
+    } else if (v == 3) {
+        colorspace = eViewerColorSpaceBT1886;
     } else {
         assert(false);
         throw std::logic_error("ViewerTab::onColorSpaceComboBoxChanged(): unknown colorspace");

diff --git a/Gui/ViewerTab30.cpp b/Gui/ViewerTab30.cpp
@@ -89,8 +89,11 @@ ViewerTab::getColorSpace() const
 
         return "Rec.709";
         break;
-    default:
+    case eViewerColorSpaceBT1886:
 
+        return "BT1886";
+        break;
+    default:
         return "";
         break;
     }