#include <assert.h>
-
+#include <Eigen/Core>
#include <Eigen/LU>
#include "colorspace_conversion_effect.h"
+#include "d65.h"
#include "util.h"
using namespace Eigen;
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;
-// The D65 white point. Given in both Rec. 601 and 709.
-static const double d65_x = 0.3127, d65_y = 0.3290;
-
ColorspaceConversionEffect::ColorspaceConversionEffect()
: source_space(COLORSPACE_sRGB),
destination_space(COLORSPACE_sRGB)
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
//
// 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
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.