Fix crash with no atmos.

[libdcp.git] / src / modified_gamma_transfer_function.cc

diff --git a/src/modified_gamma_transfer_function.cc b/src/modified_gamma_transfer_function.cc
index 7878773bdb957148977f03ea92e5913015118158..850c735118417df2c465942d9921bd222e73bcb0 100644 (file)
--- 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) {