Normalize the resample weight after bilinear combining.

[movit] / resample_effect.cpp

diff --git a/resample_effect.cpp b/resample_effect.cpp
index 6c490f141bc1a87b9f86db44b90b5d64f75d0dd7..367e8b4d52604043d6529fcdb5b392ed77136ec2 100644 (file)
--- a/resample_effect.cpp
+++ b/resample_effect.cpp
@@ -229,7 +229,6 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const str
                assert(false);
        }
 
-
        // For many resamplings (e.g. 640 -> 1280), we will end up with the same
        // set of samples over and over again in a loop. Thus, we can compute only
        // the first such loop, and then ask the card to repeat the texture for us.
@@ -305,6 +304,7 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const str
                        weights[(y * src_samples + i) * 2 + 0] = weight * radius_scaling_factor;
                        weights[(y * src_samples + i) * 2 + 1] = (src_y + 0.5) / float(src_size);
                }
+
        }
 
        // Now make use of the bilinear filtering in the GPU to reduce the number of samples
@@ -330,6 +330,18 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const str
                        src_samples,
                        src_samples - src_bilinear_samples);
                assert(int(src_samples) - int(num_samples_saved) == src_bilinear_samples);
+
+               // Normalize so that the sum becomes one. Note that we do it twice;
+               // this sometimes helps a tiny little bit when we have many samples.
+               for (int normalize_pass = 0; normalize_pass < 2; ++normalize_pass) {
+                       float sum = 0.0;
+                       for (int i = 0; i < src_bilinear_samples; ++i) {
+                               sum += bilinear_weights[(y * src_bilinear_samples + i) * 2 + 0];
+                       }
+                       for (int i = 0; i < src_bilinear_samples; ++i) {
+                               bilinear_weights[(y * src_bilinear_samples + i) * 2 + 0] /= sum;
+                       }
+               }
        }       
 
        // Encode as a two-component texture. Note the GL_REPEAT.