Factorize the code to compute sampling points for bilinear sampling into a shared...
[movit] / blur_effect.cpp
index c8cf539..90d1b68 100644 (file)
@@ -2,6 +2,7 @@
 #include <assert.h>
 
 #include "blur_effect.h"
+#include "effect_chain.h"
 #include "util.h"
 #include "opengl.h"
 
 #define NUM_TAPS 16
        
 BlurEffect::BlurEffect()
-       : radius(3.0f)
+       : radius(3.0f),
+         input_width(1280),
+         input_height(720)
 {
-       hpass = new SingleBlurPassEffect();
+       // The first blur pass will forward resolution information to us.
+       hpass = new SingleBlurPassEffect(this);
        hpass->set_int("direction", SingleBlurPassEffect::HORIZONTAL);
-       vpass = new SingleBlurPassEffect();
+       vpass = new SingleBlurPassEffect(NULL);
        vpass->set_int("direction", SingleBlurPassEffect::VERTICAL);
 
        update_radius();
 }
 
-void BlurEffect::add_self_to_effect_chain(EffectChain *chain, const std::vector<Effect *> &inputs)
+void BlurEffect::rewrite_graph(EffectChain *graph, Node *self)
 {
-       assert(inputs.size() == 1);
-       hpass->add_self_to_effect_chain(chain, inputs);
-
-       std::vector<Effect *> vpass_inputs;
-       vpass_inputs.push_back(hpass);
-       vpass->add_self_to_effect_chain(chain, vpass_inputs); 
+       Node *hpass_node = graph->add_node(hpass);
+       Node *vpass_node = graph->add_node(vpass);
+       graph->connect_nodes(hpass_node, vpass_node);
+       graph->replace_receiver(self, hpass_node);
+       graph->replace_sender(self, vpass_node);
+       self->disabled = true;
+} 
+
+// We get this information forwarded from the first blur pass,
+// since we are not part of the chain ourselves.
+void BlurEffect::inform_input_size(unsigned input_num, unsigned width, unsigned height)
+{
+       assert(input_num == 0);
+       assert(width != 0);
+       assert(height != 0);
+       input_width = width;
+       input_height = height;
+       update_radius();
 }
                
 void BlurEffect::update_radius()
@@ -34,23 +50,24 @@ void BlurEffect::update_radius()
        // We only have 16 taps to work with on each side, and we want that to
        // reach out to about 2.5*sigma. Bump up the mipmap levels (giving us
        // box blurs) until we have what we need.
-       //
-       // TODO: Consider the actual width and height (they influence mipmap
-       // sizes subtly).
-       unsigned base_mipmap_level = 0;
+       unsigned mipmap_width = input_width, mipmap_height = input_height;
        float adjusted_radius = radius;
-       while (adjusted_radius * 1.5f > NUM_TAPS / 2) {
-               ++base_mipmap_level;
-               adjusted_radius /= 2.0f;
+       while ((mipmap_width > 1 || mipmap_height > 1) && adjusted_radius * 1.5f > NUM_TAPS / 2) {
+               // Find the next mipmap size (round down, minimum 1 pixel).
+               mipmap_width = std::max(mipmap_width / 2, 1u);
+               mipmap_height = std::max(mipmap_height / 2, 1u);
+
+               // Approximate when mipmap sizes are odd, but good enough.
+               adjusted_radius = radius * float(mipmap_width) / float(input_width);
        }
        
        bool ok = hpass->set_float("radius", adjusted_radius);
-       ok |= hpass->set_int("width", 1280 / (1 << base_mipmap_level));  // FIXME
-       ok |= hpass->set_int("height", 720 / (1 << base_mipmap_level));  // FIXME
+       ok |= hpass->set_int("width", mipmap_width);
+       ok |= hpass->set_int("height", mipmap_height);
 
        ok |= vpass->set_float("radius", adjusted_radius);
-       ok |= vpass->set_int("width", 1280 / (1 << base_mipmap_level));  // FIXME
-       ok |= vpass->set_int("height", 720 / (1 << base_mipmap_level));  // FIXME
+       ok |= vpass->set_int("width", mipmap_width);
+       ok |= vpass->set_int("height", mipmap_height);
 
        assert(ok);
 }
@@ -64,8 +81,9 @@ bool BlurEffect::set_float(const std::string &key, float value) {
        return false;
 }
 
-SingleBlurPassEffect::SingleBlurPassEffect()
-       : radius(3.0f),
+SingleBlurPassEffect::SingleBlurPassEffect(BlurEffect *parent)
+       : parent(parent),
+         radius(3.0f),
          direction(HORIZONTAL),
          width(1280),
          height(720)
@@ -96,12 +114,16 @@ void SingleBlurPassEffect::set_gl_state(GLuint glsl_program_num, const std::stri
        } else {
                float sum = 0.0f;
                for (unsigned i = 0; i < NUM_TAPS + 1; ++i) {
-                       float z = i / radius;
-
                        // Gaussian blur is a common, but maybe not the prettiest choice;
                        // it can feel a bit too blurry in the fine detail and too little
                        // long-tail. This is a simple logistic distribution, which has
                        // a narrower peak but longer tails.
+                       //
+                       // We interpret the radius as sigma, similar to Gaussian blur.
+                       // Wikipedia says that sigma² = pi² s² / 3, which yields:
+                       const float s = (sqrt(3.0) / M_PI) * radius;
+                       float z = i / (2.0 * s);
+
                        weight[i] = 1.0f / (cosh(z) * cosh(z));
 
                        if (i == 0) {
@@ -140,13 +162,8 @@ void SingleBlurPassEffect::set_gl_state(GLuint glsl_program_num, const std::stri
                float w2 = weight[base_pos + 1];
 
                float offset, total_weight;
-               if (w1 + w2 < 1e-6) {
-                       offset = 0.5f;
-                       total_weight = 0.0f;
-               } else {
-                       offset = w2 / (w1 + w2);
-                       total_weight = w1 + w2;
-               }
+               combine_two_samples(w1, w2, &offset, &total_weight);
+
                float x = 0.0f, y = 0.0f;
 
                if (direction == HORIZONTAL) {