Change colourspace handling round a bit:1.0-colour-cleanup

- move the essence of GammaLUT into TransferFunction and handle
  different bit depths more neatly
- add ColourConversion to describe input gamma correction, colour
  transformation and then output gamma correction in one class.
- add default ColourConversions for sRGB->XYZ, Rec709->XYZ and
  XYZ->RGB.

2 files changed, 83 insertions, 0 deletions

diff --git a/test/colour_conversion_test.cc b/test/colour_conversion_test.cc
new file mode 100644
index 00000000..060148a6
--- /dev/null
+++ b/test/colour_conversion_test.cc
@@ -0,0 +1,82 @@
+/*
+    Copyright (C) 2014 Carl Hetherington <cth@carlh.net>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+*/
+
+#include "gamma_transfer_function.h"
+#include "colour_conversion.h"
+#include "modified_gamma_transfer_function.h"
+#include <boost/test/unit_test.hpp>
+#include <cmath>
+
+using std::pow;
+using boost::shared_ptr;
+using namespace dcp;
+
+static void
+check_gamma (shared_ptr<const TransferFunction> tf, int bit_depth, float gamma)
+{
+	float const * lut = tf->lut (bit_depth);
+	int const count = pow (2, bit_depth);
+
+	for (int i = 0; i < count; ++i) {
+		BOOST_CHECK_CLOSE (lut[i], pow (float(i) / (count - 1), gamma), 0.001);
+	}
+}
+
+static void
+check_modified_gamma (shared_ptr<const TransferFunction> tf, int bit_depth, float power, float threshold, float A, float B)
+{
+	float const * lut = tf->lut (bit_depth);
+	int const count = pow (2, bit_depth);
+
+	for (int i = 0; i < count; ++i) {
+		float const x = float(i) / (count - 1);
+		if (x > threshold) {
+			BOOST_CHECK_CLOSE (lut[i], pow ((x + A) / (1 + A), power), 0.001);
+		} else {
+			BOOST_CHECK_CLOSE (lut[i], (x / B), 0.001);
+		}
+	}
+}
+
+BOOST_AUTO_TEST_CASE (colour_conversion_test1)
+{
+	ColourConversion cc = ColourConversion::srgb_to_xyz;
+
+	check_modified_gamma (cc.in(), 8, 2.4, 0.04045, 0.055, 12.92);
+	check_modified_gamma (cc.in(), 12, 2.4, 0.04045, 0.055, 12.92);
+	check_modified_gamma (cc.in(), 16, 2.4, 0.04045, 0.055, 12.92);
+
+	check_gamma (cc.out(), 8, 2.6);
+	check_gamma (cc.out(), 12, 2.6);
+	check_gamma (cc.out(), 16, 2.6);
+}
+
+BOOST_AUTO_TEST_CASE (colour_conversion_test2)
+{
+	ColourConversion cc = ColourConversion::rec709_to_xyz;
+
+	check_modified_gamma (cc.in(), 8, 2.4, 0.081, 0.099, 4.5);
+	check_modified_gamma (cc.in(), 12, 2.4, 0.081, 0.099, 4.5);
+	check_modified_gamma (cc.in(), 16, 2.4, 0.081, 0.099, 4.5);
+
+	check_gamma (cc.out(), 8, 2.6);
+	check_gamma (cc.out(), 12, 2.6);
+	check_gamma (cc.out(), 16, 2.6);
+}
+
diff --git a/test/wscript b/test/wscript
index 0ac8b800..dbbb51d5 100644
--- a/test/wscript
+++ b/test/wscript
@@ -28,6 +28,7 @@ def build(bld):
                  argb_frame_test.cc
                  certificates_test.cc
                  colour_test.cc
+                 colour_conversion_test.cc
                  cpl_sar_test.cc
                  dcp_test.cc
                  dcp_time_test.cc