From 6de2bb3751b449abf06d44e4dda5e41b66df3f62 Mon Sep 17 00:00:00 2001
From: Carl Hetherington <cth@carlh.net>
Date: Sun, 8 May 2022 23:47:12 +0200
Subject: Extract, test and slightly adjust the piecewise LUT for inverse
 gamma.

---
 test/rgb_xyz_test.cc | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

(limited to 'test')

diff --git a/test/rgb_xyz_test.cc b/test/rgb_xyz_test.cc
index f64debc4..00787938 100644
--- a/test/rgb_xyz_test.cc
+++ b/test/rgb_xyz_test.cc
@@ -32,9 +32,10 @@
 */
 
 
-#include "rgb_xyz.h"
-#include "openjpeg_image.h"
 #include "colour_conversion.h"
+#include "openjpeg_image.h"
+#include "piecewise_lut.h"
+#include "rgb_xyz.h"
 #include "stream_operators.h"
 #include <boost/bind.hpp>
 #include <boost/random.hpp>
@@ -149,6 +150,18 @@ BOOST_AUTO_TEST_CASE (rgb_xyz_test)
 }
 
 
+/** Check the piecewise LUT that is used for inverse gamma calculation */
+BOOST_AUTO_TEST_CASE (rgb_xyz_lut_test)
+{
+	auto conversion = dcp::ColourConversion::rec709_to_xyz();
+	auto lut = dcp::make_inverse_gamma_lut(conversion.out());
+
+	for (double x = 0; x < 1; x += 0.000001) {
+		BOOST_CHECK(std::abs(lrint(lut.lookup(x) * 4095) - lrint(pow(x, 1 / 2.6) * 4095)) < 2);
+	}
+}
+
+
 static list<string> notes;
 
 static void
-- 
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