Reduce the amount of duplication between overloads in test_util.h, by using a few...

[movit] / ycbcr.cpp

diff --git a/ycbcr.cpp b/ycbcr.cpp
index 50059125dc4a3c866dff4ef08e82916d94ff7a43..59b7eed4eff496d31a653b0814ece809a148b3f4 100644 (file)
--- a/ycbcr.cpp
+++ b/ycbcr.cpp
@@ -59,7 +59,7 @@ float compute_chroma_offset(float pos, unsigned subsampling_factor, unsigned res
 // Given <ycbcr_format>, compute the values needed to turn Y'CbCr into R'G'B';
 // first subtract the returned offset, then left-multiply the returned matrix
 // (the scaling is already folded into it).
-void compute_ycbcr_matrix(YCbCrFormat ycbcr_format, float* offset, Matrix3d* ycbcr_to_rgb)
+void compute_ycbcr_matrix(YCbCrFormat ycbcr_format, float* offset, Matrix3d* ycbcr_to_rgb, GLenum type, double *scale_factor)
 {
        double coeff[3], scale[3];
 
@@ -89,25 +89,30 @@ void compute_ycbcr_matrix(YCbCrFormat ycbcr_format, float* offset, Matrix3d* ycb
                assert(false);
        }
 
+       int num_levels = ycbcr_format.num_levels;
+       if (num_levels == 0) {
+               // For the benefit of clients using old APIs, but still zeroing out the structure.
+               num_levels = 256;
+       }
        if (ycbcr_format.full_range) {
-               // TODO: Use num_levels.
-               offset[0] = 0.0 / 255.0;
-               offset[1] = 128.0 / 255.0;
-               offset[2] = 128.0 / 255.0;
+               offset[0] = 0.0 / (num_levels - 1);
+               offset[1] = double(num_levels / 2) / (num_levels - 1);  // E.g. 128/255.
+               offset[2] = double(num_levels / 2) / (num_levels - 1);
 
                scale[0] = 1.0;
                scale[1] = 1.0;
                scale[2] = 1.0;
        } else {
-               // Rec. 601, page 4; Rec. 709, page 19; Rec. 2020, page 4.
-               // TODO: Use num_levels.
-               offset[0] = 16.0 / 255.0;
-               offset[1] = 128.0 / 255.0;
-               offset[2] = 128.0 / 255.0;
-
-               scale[0] = 255.0 / 219.0;
-               scale[1] = 255.0 / 224.0;
-               scale[2] = 255.0 / 224.0;
+               // Rec. 601, page 4; Rec. 709, page 19; Rec. 2020, page 5.
+               // Rec. 2020 contains the most generic formulas, which we use here.
+               const double s = num_levels / 256.0;  // 2^(n-8) in Rec. 2020 parlance.
+               offset[0] = (s * 16.0) / (num_levels - 1);
+               offset[1] = (s * 128.0) / (num_levels - 1);
+               offset[2] = (s * 128.0) / (num_levels - 1);
+
+               scale[0] = double(num_levels - 1) / (s * 219.0);
+               scale[1] = double(num_levels - 1) / (s * 224.0);
+               scale[2] = double(num_levels - 1) / (s * 224.0);
        }
 
        // Matrix to convert RGB to YCbCr. See e.g. Rec. 601.
@@ -131,6 +136,24 @@ void compute_ycbcr_matrix(YCbCrFormat ycbcr_format, float* offset, Matrix3d* ycb
 
        // Fold in the scaling.
        *ycbcr_to_rgb *= Map<const Vector3d>(scale).asDiagonal();
+
+       if (type == GL_UNSIGNED_SHORT) {
+               // For 10-bit or 12-bit packed into 16-bit, we need to scale the values
+               // so that the max value goes from 1023 (or 4095) to 65535. We do this
+               // by folding the scaling into the conversion matrix, so it comes essentially
+               // for free. However, the offset is before the scaling (and thus assumes
+               // correctly scaled values), so we need to adjust that the other way.
+               double scale = 65535.0 / (ycbcr_format.num_levels - 1);
+               offset[0] /= scale;
+               offset[1] /= scale;
+               offset[2] /= scale;
+               *ycbcr_to_rgb *= scale;
+               if (scale_factor != nullptr) {
+                       *scale_factor = scale;
+               }
+       } else if (scale_factor != nullptr) {
+               *scale_factor = 1.0;
+       }
 }
 
 }  // namespace movit