X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=colorspace_conversion_effect.cpp;h=c14a8898f9ab2e10588479dc4601a37e34257ab4;hb=HEAD;hp=0e2425593acfe18da75824b56beb2748672c5c27;hpb=4a2924ab769a4a551a15c78336191117c03d39a8;p=movit

diff --git a/colorspace_conversion_effect.cpp b/colorspace_conversion_effect.cpp
index 0e24255..c14a889 100644
--- a/colorspace_conversion_effect.cpp
+++ b/colorspace_conversion_effect.cpp
@@ -7,6 +7,9 @@
 #include "util.h"
 
 using namespace Eigen;
+using namespace std;
+
+namespace movit {
 
 // Color coordinates from Rec. 709; sRGB uses the same primaries.
 static const double rec709_x_R = 0.640, rec709_x_G = 0.300, rec709_x_B = 0.150;
@@ -18,6 +21,10 @@ static const double rec601_525_y_R = 0.340, rec601_525_y_G = 0.595, rec601_525_y
 static const double rec601_625_x_R = 0.640, rec601_625_x_G = 0.290, rec601_625_x_B = 0.150;
 static const double rec601_625_y_R = 0.330, rec601_625_y_G = 0.600, rec601_625_y_B = 0.060;
 
+// Color coordinates from Rec. 2020.
+static const double rec2020_x_R = 0.708, rec2020_x_G = 0.170, rec2020_x_B = 0.131;
+static const double rec2020_y_R = 0.292, rec2020_y_G = 0.797, rec2020_y_B = 0.046;
+
 ColorspaceConversionEffect::ColorspaceConversionEffect()
 	: source_space(COLORSPACE_sRGB),
 	  destination_space(COLORSPACE_sRGB)
@@ -26,17 +33,33 @@ ColorspaceConversionEffect::ColorspaceConversionEffect()
 	register_int("destination_space", (int *)&destination_space);
 }
 
-Matrix3d get_xyz_matrix(Colorspace space)
+Matrix3d ColorspaceConversionEffect::get_xyz_matrix(Colorspace space)
 {
 	if (space == COLORSPACE_XYZ) {
 		return Matrix3d::Identity();
 	}
+	if (space == COLORSPACE_sRGB) {
+		// sRGB is not defined by the color primaries, but by concrete
+		// forward and inverse matrices that are rounded-off versions
+		// of the Rec. 709 color space (see
+		// https://photosauce.net/blog/post/what-makes-srgb-a-special-color-space).
+		// We're not compliant with the inverse matrix, since we'd be
+		// too accurate (sRGB is specified for 8-bit only); however,
+		// results should be very close in practice (and even closer to
+		// scRGB's inverse matrix, which is a higher-accuracy inversion of
+		// the same forward matrix).
+		return Matrix3d{
+			{ 0.4124, 0.3576, 0.1805 },
+			{ 0.2126, 0.7152, 0.0722 },
+			{ 0.0193, 0.1192, 0.9505 }
+		};
+	}
 
 	double x_R, x_G, x_B;
 	double y_R, y_G, y_B;
 
 	switch (space) {
-	case COLORSPACE_REC_709:  // And sRGB.
+	case COLORSPACE_REC_709:
 		x_R = rec709_x_R; x_G = rec709_x_G; x_B = rec709_x_B;
 		y_R = rec709_y_R; y_G = rec709_y_G; y_B = rec709_y_B;
 		break;
@@ -48,6 +71,10 @@ Matrix3d get_xyz_matrix(Colorspace space)
 		x_R = rec601_625_x_R; x_G = rec601_625_x_G; x_B = rec601_625_x_B;
 		y_R = rec601_625_y_R; y_G = rec601_625_y_G; y_B = rec601_625_y_B;
 		break;
+	case COLORSPACE_REC_2020:
+		x_R = rec2020_x_R; x_G = rec2020_x_G; x_B = rec2020_x_B;
+		y_R = rec2020_y_R; y_G = rec2020_y_G; y_B = rec2020_y_B;
+		break;
 	default:
 		assert(false);
 	}
@@ -118,7 +145,7 @@ Matrix3d get_xyz_matrix(Colorspace space)
 	return m;
 }
 
-std::string ColorspaceConversionEffect::output_fragment_shader()
+string ColorspaceConversionEffect::output_fragment_shader()
 {
 	// Create a matrix to convert from source space -> XYZ,
 	// another matrix to convert from XYZ -> destination space,
@@ -133,3 +160,5 @@ std::string ColorspaceConversionEffect::output_fragment_shader()
 	return output_glsl_mat3("PREFIX(conversion_matrix)", m) +
 		read_file("colorspace_conversion_effect.frag");
 }
+
+}  // namespace movit