X-Git-Url: https://main.carlh.net/gitweb/?a=blobdiff_plain;f=src%2Fmodified_gamma_transfer_function.cc;h=850c735118417df2c465942d9921bd222e73bcb0;hb=b872223e0652ed828dc3b4ad1eb8a0bbb34a7da0;hp=7878773bdb957148977f03ea92e5913015118158;hpb=75788462338b1b4f464d075465da3cb372c40004;p=libdcp.git

diff --git a/src/modified_gamma_transfer_function.cc b/src/modified_gamma_transfer_function.cc
index 7878773b..850c7351 100644
--- a/src/modified_gamma_transfer_function.cc
+++ b/src/modified_gamma_transfer_function.cc
@@ -25,7 +25,7 @@ using boost::shared_ptr;
 using boost::dynamic_pointer_cast;
 using namespace dcp;
 
-ModifiedGammaTransferFunction::ModifiedGammaTransferFunction (float power, float threshold, float A, float B)
+ModifiedGammaTransferFunction::ModifiedGammaTransferFunction (double power, double threshold, double A, double B)
 	: _power (power)
 	, _threshold (threshold)
 	, _A (A)
@@ -34,17 +34,29 @@ ModifiedGammaTransferFunction::ModifiedGammaTransferFunction (float power, float
 
 }
 
-float *
-ModifiedGammaTransferFunction::make_lut (int bit_depth) const
+double *
+ModifiedGammaTransferFunction::make_lut (int bit_depth, bool inverse) 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;
+	int const bit_length = int(std::pow(2.0f, bit_depth));
+	double* lut = new double[bit_length];
+	if (inverse) {
+		double const threshold = _threshold / _B;
+		for (int i = 0; i < bit_length; ++i) {
+			double const p = static_cast<double> (i) / (bit_length - 1);
+			if (p > threshold) {
+				lut[i] = (1 + _A) * pow (p, 1 / _power) - _A;
+			} else {
+				lut[i] = p * _B;
+			}
+		}
+	} else {
+		for (int i = 0; i < bit_length; ++i) {
+			double const p = static_cast<double> (i) / (bit_length - 1);
+			if (p > _threshold) {
+				lut[i] = pow ((p + _A) / (1 + _A), _power);
+			} else {
+				lut[i] = p / _B;
+			}
 		}
 	}
 
@@ -52,7 +64,7 @@ ModifiedGammaTransferFunction::make_lut (int bit_depth) const
 }
 
 bool
-ModifiedGammaTransferFunction::about_equal (shared_ptr<const TransferFunction> other, float epsilon) const
+ModifiedGammaTransferFunction::about_equal (shared_ptr<const TransferFunction> other, double epsilon) const
 {
 	shared_ptr<const ModifiedGammaTransferFunction> o = dynamic_pointer_cast<const ModifiedGammaTransferFunction> (other);
 	if (!o) {