+#include <assert.h>
+#include <Eigen/Core>
+#include <Eigen/LU>
+
#include "colorspace_conversion_effect.h"
+#include "d65.h"
#include "util.h"
-ColorSpaceConversionEffect::ColorSpaceConversionEffect()
+using namespace Eigen;
+
+// 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 rec709_y_R = 0.330, rec709_y_G = 0.600, rec709_y_B = 0.060;
+
+// Color coordinates from Rec. 601. (Separate for 525- and 625-line systems.)
+static const double rec601_525_x_R = 0.630, rec601_525_x_G = 0.310, rec601_525_x_B = 0.155;
+static const double rec601_525_y_R = 0.340, rec601_525_y_G = 0.595, rec601_525_y_B = 0.070;
+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);
}
-std::string ColorSpaceConversionEffect::output_glsl()
+Matrix3d ColorspaceConversionEffect::get_xyz_matrix(Colorspace space)
+{
+ if (space == COLORSPACE_XYZ) {
+ return Matrix3d::Identity();
+ }
+
+ double x_R, x_G, x_B;
+ double y_R, y_G, y_B;
+
+ switch (space) {
+ case COLORSPACE_REC_709: // And sRGB.
+ 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;
+ case COLORSPACE_REC_601_525:
+ x_R = rec601_525_x_R; x_G = rec601_525_x_G; x_B = rec601_525_x_B;
+ y_R = rec601_525_y_R; y_G = rec601_525_y_G; y_B = rec601_525_y_B;
+ break;
+ case COLORSPACE_REC_601_625:
+ 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);
+ }
+
+ // Recover z = 1 - x - y.
+ double z_R = 1.0 - x_R - y_R;
+ double z_G = 1.0 - x_G - y_G;
+ double z_B = 1.0 - x_B - y_B;
+
+ // We have, for each primary (example is with red):
+ //
+ // X_R / (X_R + Y_R + Z_R) = x_R
+ // Y_R / (X_R + Y_R + Z_R) = y_R
+ // Z_R / (X_R + Y_R + Z_R) = z_R
+ //
+ // Some algebraic fiddling yields (unsurprisingly):
+ //
+ // 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
+ //
+ // X_R + X_G + X_B = D65_X
+ // Y_R + Y_G + Y_B = D65_Y
+ // Z_R + Z_G + Z_B = D65_Z
+ //
+ // 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
+ // k4 Y_R + k5 Y_G + k6 Y_B = D65_Z
+ //
+ // Which we can solve for (Y_R, Y_G, Y_B) by inverting a 3x3 matrix.
+
+ Matrix3d temp;
+ temp(0,0) = x_R / y_R;
+ temp(0,1) = x_G / y_G;
+ temp(0,2) = x_B / y_B;
+
+ temp(1,0) = 1.0;
+ temp(1,1) = 1.0;
+ temp(1,2) = 1.0;
+
+ temp(2,0) = z_R / y_R;
+ temp(2,1) = z_G / y_G;
+ temp(2,2) = z_B / y_B;
+
+ Vector3d d65_XYZ(d65_X, d65_Y, d65_Z);
+ Vector3d Y_RGB = temp.inverse() * d65_XYZ;
+
+ // Now convert xyY -> XYZ.
+ double X_R = temp(0,0) * Y_RGB[0];
+ double Z_R = temp(2,0) * Y_RGB[0];
+
+ double X_G = temp(0,1) * Y_RGB[1];
+ double Z_G = temp(2,1) * Y_RGB[1];
+
+ double X_B = temp(0,2) * Y_RGB[2];
+ double Z_B = temp(2,2) * Y_RGB[2];
+
+ Matrix3d m;
+ m(0,0) = X_R; m(0,1) = X_G; m(0,2) = X_B;
+ m(1,0) = Y_RGB[0]; m(1,1) = Y_RGB[1]; m(1,2) = Y_RGB[2];
+ m(2,0) = Z_R; m(2,1) = Z_G; m(2,2) = Z_B;
+
+ return m;
+}
+
+std::string ColorspaceConversionEffect::output_fragment_shader()
{
- return read_file("todo.glsl");
+ // Create a matrix to convert from source space -> XYZ,
+ // another matrix to convert from XYZ -> destination space,
+ // and then concatenate the two.
+ //
+ // Since we right-multiply the RGB column vector, the matrix
+ // concatenation order needs to be the opposite of the operation order.
+ Matrix3d source_space_to_xyz = get_xyz_matrix(source_space);
+ Matrix3d xyz_to_destination_space = get_xyz_matrix(destination_space).inverse();
+ Matrix3d m = xyz_to_destination_space * source_space_to_xyz;
+
+ return output_glsl_mat3("PREFIX(conversion_matrix)", m) +
+ read_file("colorspace_conversion_effect.frag");
}
projects / movit / blobdiff