+
+void get_xyz_matrix(ColorSpace space, Matrix3x3 m)
+{
+ double x_R, x_G, x_B;
+ double y_R, y_G, y_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;
+ 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;
+ Y_R = rec601_Y_R; Y_G = rec601_Y_G; Y_B = rec601_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;
+ Y_R = rec601_Y_R; Y_G = rec601_Y_G; Y_B = rec601_Y_B;
+ break;
+ default:
+ assert(false);
+ }
+
+ // Convert xyY -> XYZ.
+ double X_R, X_G, X_B;
+ X_R = Y_R * x_R / y_R;
+ X_G = Y_G * x_G / y_G;
+ X_B = Y_B * x_B / y_B;
+
+ double Z_R, Z_G, Z_B;
+ Z_R = Y_R * (1.0f - x_R - y_R) / y_R;
+ Z_G = Y_G * (1.0f - x_G - y_G) / y_G;
+ Z_B = Y_B * (1.0f - x_B - y_B) / y_B;
+
+ m[0] = X_R; m[3] = X_G; m[6] = X_B;
+ m[1] = Y_R; m[4] = Y_G; m[7] = Y_B;
+ m[2] = Z_R; m[5] = Z_G; m[8] = Z_B;
+}
+
+std::string ColorSpaceConversionEffect::output_fragment_shader()
+{
+ // 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.
+ Matrix3x3 m;
+
+ Matrix3x3 source_space_to_xyz;
+ Matrix3x3 destination_space_to_xyz;
+ Matrix3x3 xyz_to_destination_space;
+
+ get_xyz_matrix(source_space, source_space_to_xyz);
+ get_xyz_matrix(destination_space, destination_space_to_xyz);
+ invert_3x3_matrix(destination_space_to_xyz, xyz_to_destination_space);
+
+ multiply_3x3_matrices(xyz_to_destination_space, source_space_to_xyz, m);
+
+ char buf[1024];
+ sprintf(buf,
+ "const mat3 PREFIX(conversion_matrix) = mat3(\n"
+ " %.8f, %.8f, %.8f,\n"
+ " %.8f, %.8f, %.8f,\n"
+ " %.8f, %.8f, %.8f);\n\n",
+ m[0], m[3], m[6],
+ m[1], m[4], m[7],
+ m[2], m[5], m[8]);
+ return buf + read_file("colorspace_conversion_effect.frag");
+}