Normalize the resample weight after bilinear combining.

[movit] / resample_effect.cpp

diff --git a/resample_effect.cpp b/resample_effect.cpp
index 264e5c10195dc65cd6bd82eca537c412bc611e7c..367e8b4d52604043d6529fcdb5b392ed77136ec2 100644 (file)
--- a/resample_effect.cpp
+++ b/resample_effect.cpp
@@ -9,9 +9,12 @@
 #include <algorithm>
 
 #include "effect_chain.h"
+#include "effect_util.h"
 #include "resample_effect.h"
 #include "util.h"
 
+using namespace std;
+
 namespace {
 
 float sinc(float x)
@@ -154,7 +157,7 @@ void ResampleEffect::update_size()
        assert(ok);
 }
 
-bool ResampleEffect::set_float(const std::string &key, float value) {
+bool ResampleEffect::set_float(const string &key, float value) {
        if (key == "width") {
                output_width = value;
                update_size();
@@ -192,7 +195,7 @@ SingleResamplePassEffect::~SingleResamplePassEffect()
        glDeleteTextures(1, &texnum);
 }
 
-std::string SingleResamplePassEffect::output_fragment_shader()
+string SingleResamplePassEffect::output_fragment_shader()
 {
        char buf[256];
        sprintf(buf, "#define DIRECTION_VERTICAL %d\n", (direction == VERTICAL));
@@ -210,8 +213,8 @@ std::string SingleResamplePassEffect::output_fragment_shader()
 // so out[0] will read from parameters <x,y> = <0,0>, <1,0>, <2,0> and so on.
 //
 // For horizontal scaling, we fill in the exact same texture;
-// the shader just interprets is differently.
-void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num)
+// the shader just interprets it differently.
+void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const string &prefix, unsigned *sampler_num)
 {
        unsigned src_size, dst_size;
        if (direction == SingleResamplePassEffect::HORIZONTAL) {
@@ -226,7 +229,6 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const std
                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.
@@ -285,7 +287,7 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const std
        // Anyhow, in this case we clearly need to look at more source pixels
        // to compute the destination pixel, and how many depend on the scaling factor.
        // Thus, the kernel width will vary with how much we scale.
-       float radius_scaling_factor = std::min(float(dst_size) / float(src_size), 1.0f);
+       float radius_scaling_factor = min(float(dst_size) / float(src_size), 1.0f);
        int int_radius = lrintf(LANCZOS_RADIUS / radius_scaling_factor);
        int src_samples = int_radius * 2 + 1;
        float *weights = new float[dst_samples * src_samples * 2];
@@ -302,6 +304,7 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const std
                        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
@@ -315,7 +318,7 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const std
        src_bilinear_samples = 0;
        for (unsigned y = 0; y < dst_samples; ++y) {
                unsigned num_samples_saved = combine_samples(weights + (y * src_samples) * 2, NULL, src_samples, UINT_MAX);
-               src_bilinear_samples = std::max<int>(src_bilinear_samples, src_samples - num_samples_saved);
+               src_bilinear_samples = max<int>(src_bilinear_samples, src_samples - num_samples_saved);
        }
 
        // Now that we know the right width, actually combine the samples.
@@ -327,6 +330,18 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const std
                        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.
@@ -347,7 +362,7 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const std
        delete[] bilinear_weights;
 }
 
-void SingleResamplePassEffect::set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num)
+void SingleResamplePassEffect::set_gl_state(GLuint glsl_program_num, const string &prefix, unsigned *sampler_num)
 {
        Effect::set_gl_state(glsl_program_num, prefix, sampler_num);