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.

1 files changed, 68 insertions, 0 deletions

diff --git a/src/modified_gamma_transfer_function.cc b/src/modified_gamma_transfer_function.cc
new file mode 100644
index 00000000..7878773b
--- /dev/null
+++ b/src/modified_gamma_transfer_function.cc
@@ -0,0 +1,68 @@
+/*
+    Copyright (C) 2012-2014 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 "modified_gamma_transfer_function.h"
+#include <cmath>
+
+using std::pow;
+using boost::shared_ptr;
+using boost::dynamic_pointer_cast;
+using namespace dcp;
+
+ModifiedGammaTransferFunction::ModifiedGammaTransferFunction (float power, float threshold, float A, float B)
+	: _power (power)
+	, _threshold (threshold)
+	, _A (A)
+	, _B (B)
+{
+
+}
+
+float *
+ModifiedGammaTransferFunction::make_lut (int bit_depth) const
+{
+	int const bit_length = pow (2, bit_depth);
+	float* lut = new float[int(std::pow(2.0f, bit_depth))];
+	for (int i = 0; i < bit_length; ++i) {
+		float const p = static_cast<float> (i) / (bit_length - 1);
+		if (p > _threshold) {
+			lut[i] = pow ((p + _A) / (1 + _A), _power);
+		} else {
+			lut[i] = p / _B;
+		}
+	}
+
+	return lut;
+}
+
+bool
+ModifiedGammaTransferFunction::about_equal (shared_ptr<const TransferFunction> other, float epsilon) const
+{
+	shared_ptr<const ModifiedGammaTransferFunction> o = dynamic_pointer_cast<const ModifiedGammaTransferFunction> (other);
+	if (!o) {
+		return false;
+	}
+
+	return (
+		fabs (_power - o->_power) < epsilon &&
+	        fabs (_threshold - o->_threshold) < epsilon &&
+		fabs (_A - o->_A) < epsilon &&
+		fabs (_B - o->_B) < epsilon
+		);
+}