Express colour conversions as chromaticities and adjust so that

everything is specified as something_to_xyz and then you can get
an inverse LUT if you want one.

1 files changed, 171 insertions, 24 deletions

diff --git a/src/colour_conversion.cc b/src/colour_conversion.cc
index 39799927..a5f77f0a 100644
--- a/src/colour_conversion.cc
+++ b/src/colour_conversion.cc
@@ -21,28 +21,45 @@
 #include "gamma_transfer_function.h"
 #include "modified_gamma_transfer_function.h"
 #include "colour_matrix.h"
+#include "dcp_assert.h"
+#include <boost/numeric/ublas/matrix.hpp>
+#include <boost/numeric/ublas/lu.hpp>
+#include <boost/numeric/ublas/io.hpp>
 
 using boost::shared_ptr;
+using boost::optional;
 using namespace dcp;
 
 ColourConversion const &
 ColourConversion::srgb_to_xyz ()
 {
 	static ColourConversion* c = new ColourConversion (
-		shared_ptr<const TransferFunction> (new ModifiedGammaTransferFunction (false, 2.4, 0.04045, 0.055, 12.92)),
-		dcp::colour_matrix::rgb_to_xyz,
-		shared_ptr<const TransferFunction> (new GammaTransferFunction (true, 2.6))
+		shared_ptr<const TransferFunction> (new ModifiedGammaTransferFunction (2.4, 0.04045, 0.055, 12.92)),
+		YUV_TO_RGB_REC601,
+		Chromaticity (0.64, 0.33),
+		Chromaticity (0.3, 0.6),
+		Chromaticity (0.15, 0.06),
+		/* D65 */
+		Chromaticity (0.3127, 0.329),
+		optional<Chromaticity> (),
+		shared_ptr<const TransferFunction> (new GammaTransferFunction (2.6))
 		);
 	return *c;
 }
 
 ColourConversion const &
-ColourConversion::xyz_to_srgb ()
+ColourConversion::rec601_to_xyz ()
 {
 	static ColourConversion* c = new ColourConversion (
-		shared_ptr<const TransferFunction> (new GammaTransferFunction (false, 2.6)),
-		dcp::colour_matrix::xyz_to_rgb,
-		shared_ptr<const TransferFunction> (new ModifiedGammaTransferFunction (true, 2.4, 0.04045, 0.055, 12.92))
+		shared_ptr<const TransferFunction> (new ModifiedGammaTransferFunction (1 / 0.45, 0.081, 0.099, 4.5)),
+		YUV_TO_RGB_REC601,
+		Chromaticity (0.64, 0.33),
+		Chromaticity (0.3, 0.6),
+		Chromaticity (0.15, 0.06),
+		/* D65 */
+		Chromaticity (0.3127, 0.329),
+		optional<Chromaticity> (),
+		shared_ptr<const TransferFunction> (new GammaTransferFunction (2.6))
 		);
 	return *c;
 }
@@ -51,39 +68,169 @@ ColourConversion const &
 ColourConversion::rec709_to_xyz ()
 {
 	static ColourConversion* c = new ColourConversion (
-		shared_ptr<const TransferFunction> (new ModifiedGammaTransferFunction (false, 1 / 0.45, 0.081, 0.099, 4.5)),
-		dcp::colour_matrix::rgb_to_xyz,
-		shared_ptr<const TransferFunction> (new GammaTransferFunction (true, 2.6))
+		shared_ptr<const TransferFunction> (new ModifiedGammaTransferFunction (1 / 0.45, 0.081, 0.099, 4.5)),
+		YUV_TO_RGB_REC709,
+		Chromaticity (0.64, 0.33),
+		Chromaticity (0.3, 0.6),
+		Chromaticity (0.15, 0.06),
+		/* D65 */
+		Chromaticity (0.3127, 0.329),
+		optional<Chromaticity> (),
+		shared_ptr<const TransferFunction> (new GammaTransferFunction (2.6))
 		);
 	return *c;
 }
 
 ColourConversion::ColourConversion (
 	shared_ptr<const TransferFunction> in,
-	double const matrix[3][3],
+	YUVToRGB yuv_to_rgb,
+	Chromaticity red,
+	Chromaticity green,
+	Chromaticity blue,
+	Chromaticity white,
+	optional<Chromaticity> adjusted_white,
 	shared_ptr<const TransferFunction> out
 	)
 	: _in (in)
-	, _matrix (3, 3)
+	, _yuv_to_rgb (yuv_to_rgb)
+	, _red (red)
+	, _green (green)
+	, _blue (blue)
+	, _white (white)
+	, _adjusted_white (adjusted_white)
 	, _out (out)
 {
-	for (int i = 0; i < 3; ++i) {
-		for (int j = 0; j < 3; ++j) {
-			_matrix (i, j) = matrix[i][j];
-		}
-	}
+	
 }
 
 bool
 ColourConversion::about_equal (ColourConversion const & other, float epsilon) const
 {
-	for (int i = 0; i < 3; ++i) {
-		for (int j = 0; j < 3; ++j) {
-			if (fabs (_matrix(i, j) - other._matrix(i, j)) > epsilon) {
-				return false;
-			}
-		}
+	if (!_in->about_equal (other._in, epsilon) ||
+	    _yuv_to_rgb != other._yuv_to_rgb ||
+	    !_red.about_equal (other._red, epsilon) ||
+	    !_green.about_equal (other._green, epsilon) ||
+	    !_blue.about_equal (other._blue, epsilon) ||
+	    !_white.about_equal (other._white, epsilon) ||
+	    !_out->about_equal (other._out, epsilon)) {
+		return false;
+	}
+
+	if (!_adjusted_white && !other._adjusted_white) {
+		return true;
+	}
+
+	if (
+		_adjusted_white && other._adjusted_white &&
+		fabs (_adjusted_white.get().x - other._adjusted_white.get().x) < epsilon &&
+		fabs (_adjusted_white.get().y - other._adjusted_white.get().y) < epsilon
+		) {
+		return true;
+	}
+
+	/* Otherwise one has an adjusted white and other hasn't, or they both have but different */
+	return false;
+}
+
+boost::numeric::ublas::matrix<double>
+ColourConversion::rgb_to_xyz () const
+{
+	/* See doc/design/colour.tex */
+
+	double const D = (_red.x - _white.x) * (_white.y - _blue.y) - (_white.x - _blue.x) * (_red.y - _white.y);
+	double const E = (_white.x - _green.x) * (_red.y - _white.y) - (_red.x - _white.x) * (_white.y - _green.y);
+	double const F = (_white.x - _green.x) * (_white.y - _blue.y) - (_white.x - _blue.x) * (_white.y - _green.y);
+	double const P = _red.y + _green.y * D / F + _blue.y * E / F;
+
+	boost::numeric::ublas::matrix<double> C (3, 3);
+	C(0, 0) = _red.x / P;
+	C(0, 1) = _green.x * D / (F * P);
+	C(0, 2) = _blue.x * E / (F * P);
+	C(1, 0) = _red.y / P;
+	C(1, 1) = _green.y * D / (F * P);
+	C(1, 2) = _blue.y * E / (F * P);
+	C(2, 0) = _red.z() / P;
+	C(2, 1) = _green.z() * D / (F * P);
+	C(2, 2) = _blue.z() * E / (F * P);
+	return C;
+}
+
+boost::numeric::ublas::matrix<double>
+ColourConversion::xyz_to_rgb () const
+{
+	boost::numeric::ublas::matrix<double> A (rgb_to_xyz ());
+
+	/* permutation matrix for the LU-factorization */
+	boost::numeric::ublas::permutation_matrix<std::size_t> pm (A.size1 ());
+
+	/* perform LU-factorization */
+	int const r = lu_factorize (A, pm);
+	DCP_ASSERT (r == 0);
+
+	/* create identity matrix of inverse */
+	boost::numeric::ublas::matrix<double> xyz_to_rgb;
+	xyz_to_rgb.assign (boost::numeric::ublas::identity_matrix<double> (A.size1 ()));
+
+	/* backsubstitute to get the inverse */
+	lu_substitute (A, pm, xyz_to_rgb);
+	
+	return xyz_to_rgb;
+}
+
+boost::numeric::ublas::matrix<double>
+ColourConversion::bradford () const
+{
+	if (!_adjusted_white || fabs (_adjusted_white.get().x) < 1e-6 || fabs (_adjusted_white.get().y) < 1e-6) {
+		boost::numeric::ublas::matrix<double> B = boost::numeric::ublas::zero_matrix<double> (3, 3);
+		B(0, 0) = 1;
+		B(1, 1) = 1;
+		B(2, 2) = 1;
+		return B;
 	}
 
-	return _in->about_equal (other._in, epsilon) && _out->about_equal (other._out, epsilon);
+	/* See doc/design/colour.tex */
+
+	boost::numeric::ublas::matrix<double> M (3, 3);
+	M(0, 0) = 0.8951;
+	M(0, 1) = 0.2664;
+	M(0, 2) = -0.1614;
+	M(1, 0) = -0.7502;
+	M(1, 1) = 1.7135;
+	M(1, 2) = 0.0367;
+	M(2, 0) = 0.0389;
+	M(2, 1) = -0.0685;
+	M(2, 2) = 1.0296;
+
+	boost::numeric::ublas::matrix<double> Mi (3, 3);
+	Mi(0, 0) = 0.9869929055;
+	Mi(0, 1) = -0.1470542564;
+	Mi(0, 2) = 0.1599626517;
+	Mi(1, 0) = 0.4323052697;
+	Mi(1, 1) = 0.5183602715;
+	Mi(1, 2) = 0.0492912282;
+	Mi(2, 0) = -0.0085286646;
+	Mi(2, 1) = 0.0400428217;
+	Mi(2, 2) = 0.9684866958;
+
+	boost::numeric::ublas::matrix<double> Gp (3, 1);
+	Gp(0, 0) = _white.x / _white.y;
+	Gp(1, 0) = 1;
+	Gp(2, 0) = (1 - _white.x - _white.y) / _white.y;
+
+	boost::numeric::ublas::matrix<double> G = boost::numeric::ublas::prod (M, Gp);
+
+	boost::numeric::ublas::matrix<double> Hp (3, 1);
+	Hp(0, 0) = _adjusted_white.get().x / _adjusted_white.get().y;
+	Hp(1, 0) = 1;
+	Hp(2, 0) = (1 - _adjusted_white.get().x - _adjusted_white.get().y) / _adjusted_white.get().y;
+
+	boost::numeric::ublas::matrix<double> H = boost::numeric::ublas::prod (M, Hp);
+
+	boost::numeric::ublas::matrix<double> C = boost::numeric::ublas::zero_matrix<double> (3, 3);
+	C(0, 0) = H(0, 0) / G(0, 0);
+	C(1, 1) = H(1, 0) / G(1, 0);
+	C(2, 2) = H(2, 0) / G(2, 0);
+
+	boost::numeric::ublas::matrix<double> CM = boost::numeric::ublas::prod (C, M);
+	return boost::numeric::ublas::prod (Mi, CM);
 }