X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=colorspace_conversion_effect.cpp;h=3f075d2b721141ef6c13428c24b93c854d4879f3;hp=9726b3b69afdb283b24cb043a9d42643a03661d2;hb=b09a4cb8dec09bcd1e42026d5b229b57e620e47c;hpb=110985baf2b42da4d5992cc7513e9f66695e4659 diff --git a/colorspace_conversion_effect.cpp b/colorspace_conversion_effect.cpp index 9726b3b..3f075d2 100644 --- a/colorspace_conversion_effect.cpp +++ b/colorspace_conversion_effect.cpp @@ -1,21 +1,26 @@ #include +#include + #include "colorspace_conversion_effect.h" #include "util.h" +using namespace Eigen; + // Color coordinates from Rec. 709; sRGB uses the same primaries. double rec709_x_R = 0.640, rec709_x_G = 0.300, rec709_x_B = 0.150; double rec709_y_R = 0.330, rec709_y_G = 0.600, rec709_y_B = 0.060; -double rec709_Y_R = 0.2126, rec709_Y_G = 0.7152, rec709_Y_B = 0.0722; // Color coordinates from Rec. 601. (Separate for 525- and 625-line systems.) double rec601_525_x_R = 0.630, rec601_525_x_G = 0.310, rec601_525_x_B = 0.155; double rec601_525_y_R = 0.340, rec601_525_y_G = 0.595, rec601_525_y_B = 0.070; double rec601_625_x_R = 0.640, rec601_625_x_G = 0.290, rec601_625_x_B = 0.150; double rec601_625_y_R = 0.330, rec601_625_y_G = 0.600, rec601_625_y_B = 0.060; -double rec601_Y_R = 0.299, rec601_Y_G = 0.587, rec601_Y_B = 0.114; -ColorSpaceConversionEffect::ColorSpaceConversionEffect() +// The D65 white point. Given in both Rec. 601 and 709. +double d65_x = 0.3127, d65_y = 0.3290; + +ColorspaceConversionEffect::ColorspaceConversionEffect() : source_space(COLORSPACE_sRGB), destination_space(COLORSPACE_sRGB) { @@ -23,49 +28,106 @@ ColorSpaceConversionEffect::ColorSpaceConversionEffect() register_int("destination_space", (int *)&destination_space); } -void get_xyz_matrix(ColorSpace space, Matrix3x3 m) +Matrix3d 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; - 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; + // 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; + + // Find the XYZ coordinates of D65 (white point for both Rec. 601 and 709), + // normalized so that Y=1. + Vector3d d65_XYZ( + d65_x / d65_y, + 1.0, + (1.0 - d65_x - d65_y) / d65_y + ); + + // 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 + // Z_R = (z_R / y_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 Y and Z by + // some constant multiple of X, 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 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() +std::string ColorspaceConversionEffect::output_fragment_shader() { // Create a matrix to convert from source space -> XYZ, // another matrix to convert from XYZ -> destination space, @@ -73,26 +135,10 @@ std::string ColorSpaceConversionEffect::output_fragment_shader() // // 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[1], m[2], - m[3], m[4], m[5], - m[6], m[7], m[8]); - return buf + read_file("colorspace_conversion_effect.frag"); + 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"); }