#include <assert.h>
-
+#include <Eigen/Core>
#include <Eigen/LU>
#include "colorspace_conversion_effect.h"
-#include "util.h"
#include "d65.h"
+#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;
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)
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;
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);
}
//
// Some algebraic fiddling yields (unsurprisingly):
//
- // X_R = (x_R / y_R) Y_R
- // Z_R = (z_R / y_R) Y_R
+ // X_R = (x_R / y_R) Y_R (so define k1 = x_R / y_R)
+ // Z_R = (z_R / y_R) Y_R (so define k4 = z_R / y_R)
//
// We also know that since RGB=(1,1,1) should give us the
// D65 illuminant, we must have
// Y_R + Y_G + Y_B = D65_Y
// Z_R + Z_G + Z_B = D65_Z
//
- // But since we already know how to express Y and Z by
- // some constant multiple of X, this reduces to
+ // But since we already know how to express X and Z by
+ // some constant multiple of Y, this reduces to
//
// k1 Y_R + k2 Y_G + k3 Y_B = D65_X
// Y_R + Y_G + Y_B = D65_Y
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,
return output_glsl_mat3("PREFIX(conversion_matrix)", m) +
read_file("colorspace_conversion_effect.frag");
}
+
+} // namespace movit