X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=colorspace_conversion_effect.cpp;h=bd4f70eb41d1d0059fab43e591b8132ef48a43f9;hp=fe8119ae76ce3a8741d106bbfc41ba9f33807d3f;hb=18fdebc534adc6b7a4c36b290b01d598bcb671bc;hpb=a88f299483ffe5068cd2828513078b9103325da8 diff --git a/colorspace_conversion_effect.cpp b/colorspace_conversion_effect.cpp index fe8119a..bd4f70e 100644 --- a/colorspace_conversion_effect.cpp +++ b/colorspace_conversion_effect.cpp @@ -1,9 +1,143 @@ +#include +#include +#include + #include "colorspace_conversion_effect.h" +#include "d65.h" +#include "util.h" + +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; -ColorSpaceConversionEffect::ColorSpaceConversionEffect() +// 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("source_space", (int *)&source_space); register_int("destination_space", (int *)&destination_space); } + +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() +{ + // 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"); +}