Rescale resampling weights so that the sum becomes one.

[movit] / resample_effect.cpp

diff --git a/resample_effect.cpp b/resample_effect.cpp
index ec4f67edad5d628dcf0b9ab555d50cb4b747b957..10dc59c5a2dbab0a0533629b801357636ad31ef0 100644 (file)
--- a/resample_effect.cpp
+++ b/resample_effect.cpp
@@ -1,14 +1,20 @@
 // Three-lobed Lanczos, the most common choice.
 #define LANCZOS_RADIUS 3.0
 
-#include <math.h>
-#include <assert.h>
 #include <GL/glew.h>
+#include <assert.h>
+#include <limits.h>
+#include <math.h>
+#include <stdio.h>
+#include <algorithm>
 
-#include "resample_effect.h"
 #include "effect_chain.h"
+#include "effect_util.h"
+#include "resample_effect.h"
 #include "util.h"
 
+using namespace std;
+
 namespace {
 
 float sinc(float x)
@@ -151,7 +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();
@@ -189,7 +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));
@@ -207,8 +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) {
@@ -282,7 +288,7 @@ 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];
@@ -293,11 +299,18 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const std
                int base_src_y = lrintf(center_src_y);
 
                // Now sample <int_radius> pixels on each side around that point.
+               double sum = 0.0;
                for (int i = 0; i < src_samples; ++i) {
                        int src_y = base_src_y + i - int_radius;
                        float weight = lanczos_weight(radius_scaling_factor * (src_y - center_src_y), LANCZOS_RADIUS);
                        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);
+                       sum += weights[(y * src_samples + i) * 2 + 0];
+               }
+
+               // Normalize so that the sum becomes one.
+               for (int i = 0; i < src_samples; ++i) {
+                       weights[(y * src_samples + i) * 2 + 0] /= sum;
                }
        }
 
@@ -312,7 +325,7 @@ 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.
@@ -344,7 +357,7 @@ 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);