Use an integer LUT for PiecewiseLUT2, hence removing a lrint and a multiply from the rgb -> xyz loop.

3 files changed, 11 insertions, 11 deletions

diff --git a/src/piecewise_lut.h b/src/piecewise_lut.h
index f2f21a92..3bea6bb8 100644
--- a/src/piecewise_lut.h
+++ b/src/piecewise_lut.h
@@ -47,24 +47,24 @@ namespace dcp {
 class PiecewiseLUT2
 {
 public:
-	PiecewiseLUT2(std::shared_ptr<const TransferFunction> fn, double boundary, int low_bits, int high_bits, bool inverse)
+	PiecewiseLUT2(std::shared_ptr<const TransferFunction> fn, double boundary, int low_bits, int high_bits, bool inverse, int scale)
 		: _boundary(boundary)
-		, _low(fn->double_lut(0, boundary, low_bits, inverse))
-		, _high(fn->double_lut(boundary, 1, high_bits, inverse))
+		, _low(fn->int_lut(0, boundary, low_bits, inverse, scale))
+		, _high(fn->int_lut(boundary, 1, high_bits, inverse, scale))
 		, _low_scale(static_cast<int>(std::pow(2.0f, low_bits)) - 1)
 		, _high_scale(static_cast<int>(std::pow(2.0f, high_bits)) - 1)
 	{
 
 	}
 
-	inline double lookup(double x) const {
+	inline int lookup(double x) const {
 		return x < _boundary ? _low[lrint((x / _boundary) * _low_scale)] : _high[lrint(((x - _boundary) / (1 - _boundary)) * _high_scale)];
 	}
 
 private:
 	double _boundary;
-	std::vector<double> _low;
-	std::vector<double> _high;
+	std::vector<int> _low;
+	std::vector<int> _high;
 	int _low_scale;
 	int _high_scale;
 };
diff --git a/src/rgb_xyz.cc b/src/rgb_xyz.cc
index cd0c7f60..9aeed761 100644
--- a/src/rgb_xyz.cc
+++ b/src/rgb_xyz.cc
@@ -262,7 +262,7 @@ PiecewiseLUT2
 dcp::make_inverse_gamma_lut(shared_ptr<const TransferFunction> fn)
 {
 	/* The parameters here were chosen by trial and error to reduce errors when running rgb_xyz_lut_test */
-	return PiecewiseLUT2(fn, 0.062, 16, 12, true);
+	return PiecewiseLUT2(fn, 0.062, 16, 12, true, 4095);
 }
 
 
@@ -323,9 +323,9 @@ rgb_to_xyz_internal(
 			d.z = min (1.0, d.z);
 
 			/* Out gamma LUT */
-			*xyz_x++ = lrint(lut_out.lookup(d.x) * 4095);
-			*xyz_y++ = lrint(lut_out.lookup(d.y) * 4095);
-			*xyz_z++ = lrint(lut_out.lookup(d.z) * 4095);
+			*xyz_x++ = lut_out.lookup(d.x);
+			*xyz_y++ = lut_out.lookup(d.y);
+			*xyz_z++ = lut_out.lookup(d.z);
 		}
 	}
 
diff --git a/test/rgb_xyz_test.cc b/test/rgb_xyz_test.cc
index cf3eb9ff..1899b1c3 100644
--- a/test/rgb_xyz_test.cc
+++ b/test/rgb_xyz_test.cc
@@ -160,7 +160,7 @@ BOOST_AUTO_TEST_CASE (rgb_xyz_lut_test)
 	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);
+		BOOST_CHECK(std::abs(lut.lookup(x) - lrint(pow(x, 1 / 2.6) * 4095)) < 2);
 	}
 }