Handle texture non-bounce a bit better.
[movit] / effect_chain.cpp
index b8361fe..0cd4802 100644 (file)
@@ -1,57 +1,97 @@
 #define GL_GLEXT_PROTOTYPES 1
 
-#include <stdio.h>
+#include <epoxy/gl.h>
+#include <assert.h>
+#include <locale.h>
 #include <math.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
-#include <assert.h>
-
 #include <algorithm>
 #include <set>
 #include <stack>
+#include <utility>
 #include <vector>
 
-#include "util.h"
+#include "alpha_division_effect.h"
+#include "alpha_multiplication_effect.h"
+#include "colorspace_conversion_effect.h"
+#include "dither_effect.h"
+#include "effect.h"
 #include "effect_chain.h"
-#include "gamma_expansion_effect.h"
 #include "gamma_compression_effect.h"
-#include "colorspace_conversion_effect.h"
+#include "gamma_expansion_effect.h"
+#include "init.h"
 #include "input.h"
-#include "opengl.h"
+#include "resource_pool.h"
+#include "util.h"
+
+using namespace std;
+
+namespace movit {
 
-EffectChain::EffectChain(float aspect_nom, float aspect_denom)
+EffectChain::EffectChain(float aspect_nom, float aspect_denom, ResourcePool *resource_pool)
        : aspect_nom(aspect_nom),
          aspect_denom(aspect_denom),
-         finalized(false) {}
+         dither_effect(NULL),
+         num_dither_bits(0),
+         finalized(false),
+         resource_pool(resource_pool) {
+       if (resource_pool == NULL) {
+               this->resource_pool = new ResourcePool();
+               owns_resource_pool = true;
+       } else {
+               owns_resource_pool = false;
+       }
+}
+
+EffectChain::~EffectChain()
+{
+       for (unsigned i = 0; i < nodes.size(); ++i) {
+               delete nodes[i]->effect;
+               delete nodes[i];
+       }
+       for (unsigned i = 0; i < phases.size(); ++i) {
+               resource_pool->release_glsl_program(phases[i]->glsl_program_num);
+               delete phases[i];
+       }
+       if (owns_resource_pool) {
+               delete resource_pool;
+       }
+}
 
 Input *EffectChain::add_input(Input *input)
 {
+       assert(!finalized);
        inputs.push_back(input);
-
-       Node *node = add_node(input);
-       node->output_color_space = input->get_color_space();
-       node->output_gamma_curve = input->get_gamma_curve();
+       add_node(input);
        return input;
 }
 
-void EffectChain::add_output(const ImageFormat &format)
+void EffectChain::add_output(const ImageFormat &format, OutputAlphaFormat alpha_format)
 {
+       assert(!finalized);
        output_format = format;
+       output_alpha_format = alpha_format;
 }
 
 Node *EffectChain::add_node(Effect *effect)
 {
-       char effect_id[256];
-       sprintf(effect_id, "eff%u", (unsigned)nodes.size());
+       for (unsigned i = 0; i < nodes.size(); ++i) {
+               assert(nodes[i]->effect != effect);
+       }
 
        Node *node = new Node;
        node->effect = effect;
        node->disabled = false;
-       node->effect_id = effect_id;
        node->output_color_space = COLORSPACE_INVALID;
        node->output_gamma_curve = GAMMA_INVALID;
+       node->output_alpha_type = ALPHA_INVALID;
 
        nodes.push_back(node);
        node_map[effect] = node;
+       effect->inform_added(this);
        return node;
 }
 
@@ -109,7 +149,7 @@ void EffectChain::insert_node_between(Node *sender, Node *middle, Node *receiver
        assert(middle->incoming_links.size() == middle->effect->num_inputs());
 }
 
-void EffectChain::find_all_nonlinear_inputs(Node *node, std::vector<Node *> *nonlinear_inputs)
+void EffectChain::find_all_nonlinear_inputs(Node *node, vector<Node *> *nonlinear_inputs)
 {
        if (node->output_gamma_curve == GAMMA_LINEAR &&
            node->effect->effect_type_id() != "GammaCompressionEffect") {
@@ -125,8 +165,9 @@ void EffectChain::find_all_nonlinear_inputs(Node *node, std::vector<Node *> *non
        }
 }
 
-Effect *EffectChain::add_effect(Effect *effect, const std::vector<Effect *> &inputs)
+Effect *EffectChain::add_effect(Effect *effect, const vector<Effect *> &inputs)
 {
+       assert(!finalized);
        assert(inputs.size() == effect->num_inputs());
        Node *node = add_node(effect);
        for (unsigned i = 0; i < inputs.size(); ++i) {
@@ -137,15 +178,15 @@ Effect *EffectChain::add_effect(Effect *effect, const std::vector<Effect *> &inp
 }
 
 // GLSL pre-1.30 doesn't support token pasting. Replace PREFIX(x) with <effect_id>_x.
-std::string replace_prefix(const std::string &text, const std::string &prefix)
+string replace_prefix(const string &text, const string &prefix)
 {
-       std::string output;
+       string output;
        size_t start = 0;
 
        while (start < text.size()) {
                size_t pos = text.find("PREFIX(", start);
-               if (pos == std::string::npos) {
-                       output.append(text.substr(start, std::string::npos));
+               if (pos == string::npos) {
+                       output.append(text.substr(start, string::npos));
                        break;
                }
 
@@ -178,47 +219,56 @@ std::string replace_prefix(const std::string &text, const std::string &prefix)
 }
 
 Phase *EffectChain::compile_glsl_program(
-       const std::vector<Node *> &inputs,
-       const std::vector<Node *> &effects)
+       const vector<Node *> &inputs,
+       const vector<Node *> &effects)
 {
+       Phase *phase = new Phase;
        assert(!effects.empty());
 
        // Deduplicate the inputs.
-       std::vector<Node *> true_inputs = inputs;
-       std::sort(true_inputs.begin(), true_inputs.end());
-       true_inputs.erase(std::unique(true_inputs.begin(), true_inputs.end()), true_inputs.end());
+       vector<Node *> true_inputs = inputs;
+       sort(true_inputs.begin(), true_inputs.end());
+       true_inputs.erase(unique(true_inputs.begin(), true_inputs.end()), true_inputs.end());
 
        bool input_needs_mipmaps = false;
-       std::string frag_shader = read_file("header.frag");
+       string frag_shader = read_file("header.frag");
 
        // Create functions for all the texture inputs that we need.
        for (unsigned i = 0; i < true_inputs.size(); ++i) {
                Node *input = true_inputs[i];
+               char effect_id[256];
+               sprintf(effect_id, "in%u", i);
+               phase->effect_ids.insert(make_pair(input, effect_id));
        
-               frag_shader += std::string("uniform sampler2D tex_") + input->effect_id + ";\n";
-               frag_shader += std::string("vec4 ") + input->effect_id + "(vec2 tc) {\n";
-               frag_shader += "\treturn texture2D(tex_" + input->effect_id + ", tc);\n";
+               frag_shader += string("uniform sampler2D tex_") + effect_id + ";\n";
+               frag_shader += string("vec4 ") + effect_id + "(vec2 tc) {\n";
+               frag_shader += "\treturn texture2D(tex_" + string(effect_id) + ", tc);\n";
                frag_shader += "}\n";
                frag_shader += "\n";
        }
 
-       for (unsigned i = 0; i < effects.size(); ++i) {
-               Node *node = effects[i];
+       vector<Node *> sorted_effects = topological_sort(effects);
+
+       for (unsigned i = 0; i < sorted_effects.size(); ++i) {
+               Node *node = sorted_effects[i];
+               char effect_id[256];
+               sprintf(effect_id, "eff%u", i);
+               phase->effect_ids.insert(make_pair(node, effect_id));
 
                if (node->incoming_links.size() == 1) {
-                       frag_shader += std::string("#define INPUT ") + node->incoming_links[0]->effect_id + "\n";
+                       frag_shader += string("#define INPUT ") + phase->effect_ids[node->incoming_links[0]] + "\n";
                } else {
                        for (unsigned j = 0; j < node->incoming_links.size(); ++j) {
                                char buf[256];
-                               sprintf(buf, "#define INPUT%d %s\n", j + 1, node->incoming_links[j]->effect_id.c_str());
+                               sprintf(buf, "#define INPUT%d %s\n", j + 1, phase->effect_ids[node->incoming_links[j]].c_str());
                                frag_shader += buf;
                        }
                }
        
                frag_shader += "\n";
-               frag_shader += std::string("#define FUNCNAME ") + node->effect_id + "\n";
-               frag_shader += replace_prefix(node->effect->output_convenience_uniforms(), node->effect_id);
-               frag_shader += replace_prefix(node->effect->output_fragment_shader(), node->effect_id);
+               frag_shader += string("#define FUNCNAME ") + effect_id + "\n";
+               frag_shader += replace_prefix(node->effect->output_convenience_uniforms(), effect_id);
+               frag_shader += replace_prefix(node->effect->output_fragment_shader(), effect_id);
                frag_shader += "#undef PREFIX\n";
                frag_shader += "#undef FUNCNAME\n";
                if (node->incoming_links.size() == 1) {
@@ -234,31 +284,19 @@ Phase *EffectChain::compile_glsl_program(
 
                input_needs_mipmaps |= node->effect->needs_mipmaps();
        }
-       for (unsigned i = 0; i < effects.size(); ++i) {
-               Node *node = effects[i];
+       for (unsigned i = 0; i < sorted_effects.size(); ++i) {
+               Node *node = sorted_effects[i];
                if (node->effect->num_inputs() == 0) {
-                       node->effect->set_int("needs_mipmaps", input_needs_mipmaps);
+                       CHECK(node->effect->set_int("needs_mipmaps", input_needs_mipmaps));
                }
        }
-       frag_shader += std::string("#define INPUT ") + effects.back()->effect_id + "\n";
+       frag_shader += string("#define INPUT ") + phase->effect_ids[sorted_effects.back()] + "\n";
        frag_shader.append(read_file("footer.frag"));
-       printf("%s\n", frag_shader.c_str());
-       
-       GLuint glsl_program_num = glCreateProgram();
-       GLuint vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
-       GLuint fs_obj = compile_shader(frag_shader, GL_FRAGMENT_SHADER);
-       glAttachShader(glsl_program_num, vs_obj);
-       check_error();
-       glAttachShader(glsl_program_num, fs_obj);
-       check_error();
-       glLinkProgram(glsl_program_num);
-       check_error();
 
-       Phase *phase = new Phase;
-       phase->glsl_program_num = glsl_program_num;
+       phase->glsl_program_num = resource_pool->compile_glsl_program(read_file("vs.vert"), frag_shader);
        phase->input_needs_mipmaps = input_needs_mipmaps;
        phase->inputs = true_inputs;
-       phase->effects = effects;
+       phase->effects = sorted_effects;
 
        return phase;
 }
@@ -273,25 +311,25 @@ Phase *EffectChain::compile_glsl_program(
 // without any explicit recursion.
 void EffectChain::construct_glsl_programs(Node *output)
 {
-       // Which effects have already been completed in this phase?
+       // Which effects have already been completed?
        // We need to keep track of it, as an effect with multiple outputs
-       // could otherwise be calculate multiple times.
-       std::set<Node *> completed_effects;
+       // could otherwise be calculated multiple times.
+       set<Node *> completed_effects;
 
        // Effects in the current phase, as well as inputs (outputs from other phases
        // that we depend on). Note that since we start iterating from the end,
        // the effect list will be in the reverse order.
-       std::vector<Node *> this_phase_inputs;
-       std::vector<Node *> this_phase_effects;
+       vector<Node *> this_phase_inputs;
+       vector<Node *> this_phase_effects;
 
        // Effects that we have yet to calculate, but that we know should
        // be in the current phase.
-       std::stack<Node *> effects_todo_this_phase;
+       stack<Node *> effects_todo_this_phase;
 
        // Effects that we have yet to calculate, but that come from other phases.
        // We delay these until we have this phase done in its entirety,
        // at which point we pick any of them and start a new phase from that.
-       std::stack<Node *> effects_todo_other_phases;
+       stack<Node *> effects_todo_other_phases;
 
        effects_todo_this_phase.push(output);
 
@@ -301,31 +339,54 @@ void EffectChain::construct_glsl_programs(Node *output)
                        Node *node = effects_todo_this_phase.top();
                        effects_todo_this_phase.pop();
 
-                       // This should currently only happen for effects that are phase outputs,
-                       // and we throw those out separately below.
-                       assert(completed_effects.count(node) == 0);
+                       // This should currently only happen for effects that are inputs
+                       // (either true inputs or phase outputs). We special-case inputs,
+                       // and then deduplicate phase outputs in compile_glsl_program().
+                       if (node->effect->num_inputs() == 0) {
+                               if (find(this_phase_effects.begin(), this_phase_effects.end(), node) != this_phase_effects.end()) {
+                                       continue;
+                               }
+                       } else {
+                               assert(completed_effects.count(node) == 0);
+                       }
 
                        this_phase_effects.push_back(node);
                        completed_effects.insert(node);
 
                        // Find all the dependencies of this effect, and add them to the stack.
-                       std::vector<Node *> deps = node->incoming_links;
+                       vector<Node *> deps = node->incoming_links;
                        assert(node->effect->num_inputs() == deps.size());
                        for (unsigned i = 0; i < deps.size(); ++i) {
                                bool start_new_phase = false;
 
-                               // FIXME: If we sample directly from a texture, we won't need this.
-                               if (node->effect->needs_texture_bounce()) {
+                               if (node->effect->needs_texture_bounce() &&
+                                   !deps[i]->effect->is_single_texture()) {
                                        start_new_phase = true;
                                }
 
-                               if (deps[i]->outgoing_links.size() > 1 && deps[i]->effect->num_inputs() > 0) {
-                                       // More than one effect uses this as the input,
-                                       // and it is not a texture itself.
-                                       // The easiest thing to do (and probably also the safest
-                                       // performance-wise in most cases) is to bounce it to a texture
-                                       // and then let the next passes read from that.
-                                       start_new_phase = true;
+                               if (deps[i]->outgoing_links.size() > 1) {
+                                       if (!deps[i]->effect->is_single_texture()) {
+                                               // More than one effect uses this as the input,
+                                               // and it is not a texture itself.
+                                               // The easiest thing to do (and probably also the safest
+                                               // performance-wise in most cases) is to bounce it to a texture
+                                               // and then let the next passes read from that.
+                                               start_new_phase = true;
+                                       } else {
+                                               assert(deps[i]->effect->num_inputs() == 0);
+
+                                               // For textures, we try to be slightly more clever;
+                                               // if none of our outputs need a bounce, we don't bounce
+                                               // but instead simply use the effect many times.
+                                               //
+                                               // Strictly speaking, we could bounce it for some outputs
+                                               // and use it directly for others, but the processing becomes
+                                               // somewhat simpler if the effect is only used in one such way.
+                                               for (unsigned j = 0; j < deps[i]->outgoing_links.size(); ++j) {
+                                                       Node *rdep = deps[i]->outgoing_links[j];
+                                                       start_new_phase |= rdep->effect->needs_texture_bounce();
+                                               }
+                                       }
                                }
 
                                if (deps[i]->effect->changes_output_size()) {
@@ -370,11 +431,15 @@ void EffectChain::construct_glsl_programs(Node *output)
 
        // Finally, since the phases are found from the output but must be executed
        // from the input(s), reverse them, too.
-       std::reverse(phases.begin(), phases.end());
+       reverse(phases.begin(), phases.end());
 }
 
 void EffectChain::output_dot(const char *filename)
 {
+       if (movit_debug_level != MOVIT_DEBUG_ON) {
+               return;
+       }
+
        FILE *fp = fopen(filename, "w");
        if (fp == NULL) {
                perror(filename);
@@ -382,55 +447,46 @@ void EffectChain::output_dot(const char *filename)
        }
 
        fprintf(fp, "digraph G {\n");
+       fprintf(fp, "  output [shape=box label=\"(output)\"];\n");
        for (unsigned i = 0; i < nodes.size(); ++i) {
-               fprintf(fp, "  n%ld [label=\"%s\"];\n", (long)nodes[i], nodes[i]->effect->effect_type_id().c_str());
-               for (unsigned j = 0; j < nodes[i]->outgoing_links.size(); ++j) {
-                       std::vector<std::string> labels;
-
-                       if (nodes[i]->outgoing_links[j]->effect->needs_texture_bounce()) {
-                               labels.push_back("needs_bounce");
-                       }
-                       if (nodes[i]->effect->changes_output_size()) {
-                               labels.push_back("resize");
+               // Find out which phase this event belongs to.
+               vector<int> in_phases;
+               for (unsigned j = 0; j < phases.size(); ++j) {
+                       const Phase* p = phases[j];
+                       if (find(p->effects.begin(), p->effects.end(), nodes[i]) != p->effects.end()) {
+                               in_phases.push_back(j);
                        }
+               }
 
-                       switch (nodes[i]->output_color_space) {
-                       case COLORSPACE_INVALID:
-                               labels.push_back("spc[invalid]");
-                               break;
-                       case COLORSPACE_REC_601_525:
-                               labels.push_back("spc[rec601-525]");
-                               break;
-                       case COLORSPACE_REC_601_625:
-                               labels.push_back("spc[rec601-625]");
-                               break;
-                       default:
-                               break;
-                       }
+               if (in_phases.empty()) {
+                       fprintf(fp, "  n%ld [label=\"%s\"];\n", (long)nodes[i], nodes[i]->effect->effect_type_id().c_str());
+               } else if (in_phases.size() == 1) {
+                       fprintf(fp, "  n%ld [label=\"%s\" style=\"filled\" fillcolor=\"/accent8/%d\"];\n",
+                               (long)nodes[i], nodes[i]->effect->effect_type_id().c_str(),
+                               (in_phases[0] % 8) + 1);
+               } else {
+                       // If we had new enough Graphviz, style="wedged" would probably be ideal here.
+                       // But alas.
+                       fprintf(fp, "  n%ld [label=\"%s [in multiple phases]\" style=\"filled\" fillcolor=\"/accent8/%d\"];\n",
+                               (long)nodes[i], nodes[i]->effect->effect_type_id().c_str(),
+                               (in_phases[0] % 8) + 1);
+               }
 
-                       switch (nodes[i]->output_gamma_curve) {
-                       case GAMMA_INVALID:
-                               labels.push_back("gamma[invalid]");
-                               break;
-                       case GAMMA_sRGB:
-                               labels.push_back("gamma[sRGB]");
-                               break;
-                       case GAMMA_REC_601:  // and GAMMA_REC_709
-                               labels.push_back("gamma[rec601/709]");
-                               break;
-                       default:
-                               break;
-                       }
+               char from_node_id[256];
+               snprintf(from_node_id, 256, "n%ld", (long)nodes[i]);
 
-                       if (labels.empty()) {
-                               fprintf(fp, "  n%ld -> n%ld;\n", (long)nodes[i], (long)nodes[i]->outgoing_links[j]);
-                       } else {
-                               std::string label = labels[0];
-                               for (unsigned k = 1; k < labels.size(); ++k) {
-                                       label += ", " + labels[k];
-                               }
-                               fprintf(fp, "  n%ld -> n%ld [label=\"%s\"];\n", (long)nodes[i], (long)nodes[i]->outgoing_links[j], label.c_str());
-                       }
+               for (unsigned j = 0; j < nodes[i]->outgoing_links.size(); ++j) {
+                       char to_node_id[256];
+                       snprintf(to_node_id, 256, "n%ld", (long)nodes[i]->outgoing_links[j]);
+
+                       vector<string> labels = get_labels_for_edge(nodes[i], nodes[i]->outgoing_links[j]);
+                       output_dot_edge(fp, from_node_id, to_node_id, labels);
+               }
+
+               if (nodes[i]->outgoing_links.empty() && !nodes[i]->disabled) {
+                       // Output node.
+                       vector<string> labels = get_labels_for_edge(nodes[i], NULL);
+                       output_dot_edge(fp, from_node_id, "output", labels);
                }
        }
        fprintf(fp, "}\n");
@@ -438,16 +494,102 @@ void EffectChain::output_dot(const char *filename)
        fclose(fp);
 }
 
-unsigned EffectChain::fit_rectangle_to_aspect(unsigned width, unsigned height)
+vector<string> EffectChain::get_labels_for_edge(const Node *from, const Node *to)
 {
+       vector<string> labels;
+
+       if (to != NULL && to->effect->needs_texture_bounce()) {
+               labels.push_back("needs_bounce");
+       }
+       if (from->effect->changes_output_size()) {
+               labels.push_back("resize");
+       }
+
+       switch (from->output_color_space) {
+       case COLORSPACE_INVALID:
+               labels.push_back("spc[invalid]");
+               break;
+       case COLORSPACE_REC_601_525:
+               labels.push_back("spc[rec601-525]");
+               break;
+       case COLORSPACE_REC_601_625:
+               labels.push_back("spc[rec601-625]");
+               break;
+       default:
+               break;
+       }
+
+       switch (from->output_gamma_curve) {
+       case GAMMA_INVALID:
+               labels.push_back("gamma[invalid]");
+               break;
+       case GAMMA_sRGB:
+               labels.push_back("gamma[sRGB]");
+               break;
+       case GAMMA_REC_601:  // and GAMMA_REC_709
+               labels.push_back("gamma[rec601/709]");
+               break;
+       default:
+               break;
+       }
+
+       switch (from->output_alpha_type) {
+       case ALPHA_INVALID:
+               labels.push_back("alpha[invalid]");
+               break;
+       case ALPHA_BLANK:
+               labels.push_back("alpha[blank]");
+               break;
+       case ALPHA_POSTMULTIPLIED:
+               labels.push_back("alpha[postmult]");
+               break;
+       default:
+               break;
+       }
+
+       return labels;
+}
+
+void EffectChain::output_dot_edge(FILE *fp,
+                                  const string &from_node_id,
+                                  const string &to_node_id,
+                                  const vector<string> &labels)
+{
+       if (labels.empty()) {
+               fprintf(fp, "  %s -> %s;\n", from_node_id.c_str(), to_node_id.c_str());
+       } else {
+               string label = labels[0];
+               for (unsigned k = 1; k < labels.size(); ++k) {
+                       label += ", " + labels[k];
+               }
+               fprintf(fp, "  %s -> %s [label=\"%s\"];\n", from_node_id.c_str(), to_node_id.c_str(), label.c_str());
+       }
+}
+
+void EffectChain::size_rectangle_to_fit(unsigned width, unsigned height, unsigned *output_width, unsigned *output_height)
+{
+       unsigned scaled_width, scaled_height;
+
        if (float(width) * aspect_denom >= float(height) * aspect_nom) {
                // Same aspect, or W/H > aspect (image is wider than the frame).
-               // In either case, keep width.
-               return width;
+               // In either case, keep width, and adjust height.
+               scaled_width = width;
+               scaled_height = lrintf(width * aspect_denom / aspect_nom);
        } else {
                // W/H < aspect (image is taller than the frame), so keep height,
-               // and adjust width correspondingly.
-               return lrintf(height * aspect_nom / aspect_denom);
+               // and adjust width.
+               scaled_width = lrintf(height * aspect_nom / aspect_denom);
+               scaled_height = height;
+       }
+
+       // We should be consistently larger or smaller then the existing choice,
+       // since we have the same aspect.
+       assert(!(scaled_width < *output_width && scaled_height > *output_height));
+       assert(!(scaled_height < *output_height && scaled_width > *output_width));
+
+       if (scaled_width >= *output_width && scaled_height >= *output_height) {
+               *output_width = scaled_width;
+               *output_height = scaled_height;
        }
 }
 
@@ -471,8 +613,8 @@ void EffectChain::inform_input_sizes(Phase *phase)
        }
        for (unsigned i = 0; i < phase->inputs.size(); ++i) {
                Node *input = phase->inputs[i];
-               input->output_width = input->phase->output_width;
-               input->output_height = input->phase->output_height;
+               input->output_width = input->phase->virtual_output_width;
+               input->output_height = input->phase->virtual_output_height;
                assert(input->output_width != 0);
                assert(input->output_height != 0);
        }
@@ -515,20 +657,25 @@ void EffectChain::find_output_size(Phase *phase)
 
        // If the last effect explicitly sets an output size, use that.
        if (output_node->effect->changes_output_size()) {
-               output_node->effect->get_output_size(&phase->output_width, &phase->output_height);
+               output_node->effect->get_output_size(&phase->output_width, &phase->output_height,
+                                                    &phase->virtual_output_width, &phase->virtual_output_height);
                return;
        }
 
-       // If not, look at the input phases and textures.
-       // We select the largest one (by fit into the current aspect).
-       unsigned best_width = 0;
+       // If all effects have the same size, use that.
+       unsigned output_width = 0, output_height = 0;
+       bool all_inputs_same_size = true;
+
        for (unsigned i = 0; i < phase->inputs.size(); ++i) {
                Node *input = phase->inputs[i];
                assert(input->phase->output_width != 0);
                assert(input->phase->output_height != 0);
-               unsigned width = fit_rectangle_to_aspect(input->phase->output_width, input->phase->output_height);
-               if (width > best_width) {
-                       best_width = width;
+               if (output_width == 0 && output_height == 0) {
+                       output_width = input->phase->virtual_output_width;
+                       output_height = input->phase->virtual_output_height;
+               } else if (output_width != input->phase->virtual_output_width ||
+                          output_height != input->phase->virtual_output_height) {
+                       all_inputs_same_size = false;
                }
        }
        for (unsigned i = 0; i < phase->effects.size(); ++i) {
@@ -538,48 +685,118 @@ void EffectChain::find_output_size(Phase *phase)
                }
 
                Input *input = static_cast<Input *>(effect);
-               unsigned width = fit_rectangle_to_aspect(input->get_width(), input->get_height());
-               if (width > best_width) {
-                       best_width = width;
+               if (output_width == 0 && output_height == 0) {
+                       output_width = input->get_width();
+                       output_height = input->get_height();
+               } else if (output_width != input->get_width() ||
+                          output_height != input->get_height()) {
+                       all_inputs_same_size = false;
                }
        }
-       assert(best_width != 0);
-       phase->output_width = best_width;
-       phase->output_height = best_width * aspect_denom / aspect_nom;
+
+       if (all_inputs_same_size) {
+               assert(output_width != 0);
+               assert(output_height != 0);
+               phase->virtual_output_width = phase->output_width = output_width;
+               phase->virtual_output_height = phase->output_height = output_height;
+               return;
+       }
+
+       // If not, fit all the inputs into the current aspect, and select the largest one. 
+       output_width = 0;
+       output_height = 0;
+       for (unsigned i = 0; i < phase->inputs.size(); ++i) {
+               Node *input = phase->inputs[i];
+               assert(input->phase->output_width != 0);
+               assert(input->phase->output_height != 0);
+               size_rectangle_to_fit(input->phase->output_width, input->phase->output_height, &output_width, &output_height);
+       }
+       for (unsigned i = 0; i < phase->effects.size(); ++i) {
+               Effect *effect = phase->effects[i]->effect;
+               if (effect->num_inputs() != 0) {
+                       continue;
+               }
+
+               Input *input = static_cast<Input *>(effect);
+               size_rectangle_to_fit(input->get_width(), input->get_height(), &output_width, &output_height);
+       }
+       assert(output_width != 0);
+       assert(output_height != 0);
+       phase->virtual_output_width = phase->output_width = output_width;
+       phase->virtual_output_height = phase->output_height = output_height;
 }
 
-void EffectChain::sort_nodes_topologically()
+void EffectChain::sort_all_nodes_topologically()
 {
-       std::set<Node *> visited_nodes;
-       std::vector<Node *> sorted_list;
+       nodes = topological_sort(nodes);
+}
+
+vector<Node *> EffectChain::topological_sort(const vector<Node *> &nodes)
+{
+       set<Node *> nodes_left_to_visit(nodes.begin(), nodes.end());
+       vector<Node *> sorted_list;
        for (unsigned i = 0; i < nodes.size(); ++i) {
-               if (nodes[i]->incoming_links.size() == 0) {
-                       topological_sort_visit_node(nodes[i], &visited_nodes, &sorted_list);
-               }
+               topological_sort_visit_node(nodes[i], &nodes_left_to_visit, &sorted_list);
        }
        reverse(sorted_list.begin(), sorted_list.end());
-       nodes = sorted_list;
+       return sorted_list;
 }
 
-void EffectChain::topological_sort_visit_node(Node *node, std::set<Node *> *visited_nodes, std::vector<Node *> *sorted_list)
+void EffectChain::topological_sort_visit_node(Node *node, set<Node *> *nodes_left_to_visit, vector<Node *> *sorted_list)
 {
-       if (visited_nodes->count(node) != 0) {
+       if (nodes_left_to_visit->count(node) == 0) {
                return;
        }
-       visited_nodes->insert(node);
+       nodes_left_to_visit->erase(node);
        for (unsigned i = 0; i < node->outgoing_links.size(); ++i) {
-               topological_sort_visit_node(node->outgoing_links[i], visited_nodes, sorted_list);
+               topological_sort_visit_node(node->outgoing_links[i], nodes_left_to_visit, sorted_list);
        }
        sorted_list->push_back(node);
 }
 
+void EffectChain::find_color_spaces_for_inputs()
+{
+       for (unsigned i = 0; i < nodes.size(); ++i) {
+               Node *node = nodes[i];
+               if (node->disabled) {
+                       continue;
+               }
+               if (node->incoming_links.size() == 0) {
+                       Input *input = static_cast<Input *>(node->effect);
+                       node->output_color_space = input->get_color_space();
+                       node->output_gamma_curve = input->get_gamma_curve();
+
+                       Effect::AlphaHandling alpha_handling = input->alpha_handling();
+                       switch (alpha_handling) {
+                       case Effect::OUTPUT_BLANK_ALPHA:
+                               node->output_alpha_type = ALPHA_BLANK;
+                               break;
+                       case Effect::INPUT_AND_OUTPUT_PREMULTIPLIED_ALPHA:
+                               node->output_alpha_type = ALPHA_PREMULTIPLIED;
+                               break;
+                       case Effect::OUTPUT_POSTMULTIPLIED_ALPHA:
+                               node->output_alpha_type = ALPHA_POSTMULTIPLIED;
+                               break;
+                       case Effect::INPUT_PREMULTIPLIED_ALPHA_KEEP_BLANK:
+                       case Effect::DONT_CARE_ALPHA_TYPE:
+                       default:
+                               assert(false);
+                       }
+
+                       if (node->output_alpha_type == ALPHA_PREMULTIPLIED) {
+                               assert(node->output_gamma_curve == GAMMA_LINEAR);
+                       }
+               }
+       }
+}
+
 // Propagate gamma and color space information as far as we can in the graph.
 // The rules are simple: Anything where all the inputs agree, get that as
 // output as well. Anything else keeps having *_INVALID.
 void EffectChain::propagate_gamma_and_color_space()
 {
        // We depend on going through the nodes in order.
-       sort_nodes_topologically();
+       sort_all_nodes_topologically();
 
        for (unsigned i = 0; i < nodes.size(); ++i) {
                Node *node = nodes[i];
@@ -593,7 +810,7 @@ void EffectChain::propagate_gamma_and_color_space()
                        continue;
                }
 
-               ColorSpace color_space = node->incoming_links[0]->output_color_space;
+               Colorspace color_space = node->incoming_links[0]->output_color_space;
                GammaCurve gamma_curve = node->incoming_links[0]->output_gamma_curve;
                for (unsigned j = 1; j < node->incoming_links.size(); ++j) {
                        if (node->incoming_links[j]->output_color_space != color_space) {
@@ -606,7 +823,7 @@ void EffectChain::propagate_gamma_and_color_space()
 
                // The conversion effects already have their outputs set correctly,
                // so leave them alone.
-               if (node->effect->effect_type_id() != "ColorSpaceConversionEffect") {
+               if (node->effect->effect_type_id() != "ColorspaceConversionEffect") {
                        node->output_color_space = color_space;
                }               
                if (node->effect->effect_type_id() != "GammaCompressionEffect" &&
@@ -616,6 +833,130 @@ void EffectChain::propagate_gamma_and_color_space()
        }
 }
 
+// Propagate alpha information as far as we can in the graph.
+// Similar to propagate_gamma_and_color_space().
+void EffectChain::propagate_alpha()
+{
+       // We depend on going through the nodes in order.
+       sort_all_nodes_topologically();
+
+       for (unsigned i = 0; i < nodes.size(); ++i) {
+               Node *node = nodes[i];
+               if (node->disabled) {
+                       continue;
+               }
+               assert(node->incoming_links.size() == node->effect->num_inputs());
+               if (node->incoming_links.size() == 0) {
+                       assert(node->output_alpha_type != ALPHA_INVALID);
+                       continue;
+               }
+
+               // The alpha multiplication/division effects are special cases.
+               if (node->effect->effect_type_id() == "AlphaMultiplicationEffect") {
+                       assert(node->incoming_links.size() == 1);
+                       assert(node->incoming_links[0]->output_alpha_type == ALPHA_POSTMULTIPLIED);
+                       node->output_alpha_type = ALPHA_PREMULTIPLIED;
+                       continue;
+               }
+               if (node->effect->effect_type_id() == "AlphaDivisionEffect") {
+                       assert(node->incoming_links.size() == 1);
+                       assert(node->incoming_links[0]->output_alpha_type == ALPHA_PREMULTIPLIED);
+                       node->output_alpha_type = ALPHA_POSTMULTIPLIED;
+                       continue;
+               }
+
+               // GammaCompressionEffect and GammaExpansionEffect are also a special case,
+               // because they are the only one that _need_ postmultiplied alpha.
+               if (node->effect->effect_type_id() == "GammaCompressionEffect" ||
+                   node->effect->effect_type_id() == "GammaExpansionEffect") {
+                       assert(node->incoming_links.size() == 1);
+                       if (node->incoming_links[0]->output_alpha_type == ALPHA_BLANK) {
+                               node->output_alpha_type = ALPHA_BLANK;
+                       } else if (node->incoming_links[0]->output_alpha_type == ALPHA_POSTMULTIPLIED) {
+                               node->output_alpha_type = ALPHA_POSTMULTIPLIED;
+                       } else {
+                               node->output_alpha_type = ALPHA_INVALID;
+                       }
+                       continue;
+               }
+
+               // Only inputs can have unconditional alpha output (OUTPUT_BLANK_ALPHA
+               // or OUTPUT_POSTMULTIPLIED_ALPHA), and they have already been
+               // taken care of above. Rationale: Even if you could imagine
+               // e.g. an effect that took in an image and set alpha=1.0
+               // unconditionally, it wouldn't make any sense to have it as
+               // e.g. OUTPUT_BLANK_ALPHA, since it wouldn't know whether it
+               // got its input pre- or postmultiplied, so it wouldn't know
+               // whether to divide away the old alpha or not.
+               Effect::AlphaHandling alpha_handling = node->effect->alpha_handling();
+               assert(alpha_handling == Effect::INPUT_AND_OUTPUT_PREMULTIPLIED_ALPHA ||
+                      alpha_handling == Effect::INPUT_PREMULTIPLIED_ALPHA_KEEP_BLANK ||
+                      alpha_handling == Effect::DONT_CARE_ALPHA_TYPE);
+
+               // If the node has multiple inputs, check that they are all valid and
+               // the same.
+               bool any_invalid = false;
+               bool any_premultiplied = false;
+               bool any_postmultiplied = false;
+
+               for (unsigned j = 0; j < node->incoming_links.size(); ++j) {
+                       switch (node->incoming_links[j]->output_alpha_type) {
+                       case ALPHA_INVALID:
+                               any_invalid = true;
+                               break;
+                       case ALPHA_BLANK:
+                               // Blank is good as both pre- and postmultiplied alpha,
+                               // so just ignore it.
+                               break;
+                       case ALPHA_PREMULTIPLIED:
+                               any_premultiplied = true;
+                               break;
+                       case ALPHA_POSTMULTIPLIED:
+                               any_postmultiplied = true;
+                               break;
+                       default:
+                               assert(false);
+                       }
+               }
+
+               if (any_invalid) {
+                       node->output_alpha_type = ALPHA_INVALID;
+                       continue;
+               }
+
+               // Inputs must be of the same type.
+               if (any_premultiplied && any_postmultiplied) {
+                       node->output_alpha_type = ALPHA_INVALID;
+                       continue;
+               }
+
+               if (alpha_handling == Effect::INPUT_AND_OUTPUT_PREMULTIPLIED_ALPHA ||
+                   alpha_handling == Effect::INPUT_PREMULTIPLIED_ALPHA_KEEP_BLANK) {
+                       // If the effect has asked for premultiplied alpha, check that it has got it.
+                       if (any_postmultiplied) {
+                               node->output_alpha_type = ALPHA_INVALID;
+                       } else if (!any_premultiplied &&
+                                  alpha_handling == Effect::INPUT_PREMULTIPLIED_ALPHA_KEEP_BLANK) {
+                               // Blank input alpha, and the effect preserves blank alpha.
+                               node->output_alpha_type = ALPHA_BLANK;
+                       } else {
+                               node->output_alpha_type = ALPHA_PREMULTIPLIED;
+                       }
+               } else {
+                       // OK, all inputs are the same, and this effect is not going
+                       // to change it.
+                       assert(alpha_handling == Effect::DONT_CARE_ALPHA_TYPE);
+                       if (any_premultiplied) {
+                               node->output_alpha_type = ALPHA_PREMULTIPLIED;
+                       } else if (any_postmultiplied) {
+                               node->output_alpha_type = ALPHA_POSTMULTIPLIED;
+                       } else {
+                               node->output_alpha_type = ALPHA_BLANK;
+                       }
+               }
+       }
+}
+
 bool EffectChain::node_needs_colorspace_fix(Node *node)
 {
        if (node->disabled) {
@@ -653,18 +994,19 @@ void EffectChain::fix_internal_color_spaces()
                        }
 
                        // Go through each input that is not sRGB, and insert
-                       // a colorspace conversion before it.
+                       // a colorspace conversion after it.
                        for (unsigned j = 0; j < node->incoming_links.size(); ++j) {
                                Node *input = node->incoming_links[j];
                                assert(input->output_color_space != COLORSPACE_INVALID);
                                if (input->output_color_space == COLORSPACE_sRGB) {
                                        continue;
                                }
-                               Node *conversion = add_node(new ColorSpaceConversionEffect());
-                               conversion->effect->set_int("source_space", input->output_color_space);
-                               conversion->effect->set_int("destination_space", COLORSPACE_sRGB);
+                               Node *conversion = add_node(new ColorspaceConversionEffect());
+                               CHECK(conversion->effect->set_int("source_space", input->output_color_space));
+                               CHECK(conversion->effect->set_int("destination_space", COLORSPACE_sRGB));
                                conversion->output_color_space = COLORSPACE_sRGB;
-                               insert_node_between(input, conversion, node);
+                               replace_sender(input, conversion);
+                               connect_nodes(input, conversion);
                        }
 
                        // Re-sort topologically, and propagate the new information.
@@ -675,7 +1017,7 @@ void EffectChain::fix_internal_color_spaces()
                }
        
                char filename[256];
-               sprintf(filename, "step3-colorspacefix-iter%u.dot", ++colorspace_propagation_pass);
+               sprintf(filename, "step5-colorspacefix-iter%u.dot", ++colorspace_propagation_pass);
                output_dot(filename);
                assert(colorspace_propagation_pass < 100);
        } while (found_any);
@@ -689,16 +1031,125 @@ void EffectChain::fix_internal_color_spaces()
        }
 }
 
+bool EffectChain::node_needs_alpha_fix(Node *node)
+{
+       if (node->disabled) {
+               return false;
+       }
+
+       // propagate_alpha() has already set our output to ALPHA_INVALID if the
+       // inputs differ or we are otherwise in mismatch, so we can rely on that.
+       return (node->output_alpha_type == ALPHA_INVALID);
+}
+
+// Fix up alpha so that there are no ALPHA_INVALID nodes left in
+// the graph. Similar to fix_internal_color_spaces().
+void EffectChain::fix_internal_alpha(unsigned step)
+{
+       unsigned alpha_propagation_pass = 0;
+       bool found_any;
+       do {
+               found_any = false;
+               for (unsigned i = 0; i < nodes.size(); ++i) {
+                       Node *node = nodes[i];
+                       if (!node_needs_alpha_fix(node)) {
+                               continue;
+                       }
+
+                       // If we need to fix up GammaExpansionEffect, then clearly something
+                       // is wrong, since the combination of premultiplied alpha and nonlinear inputs
+                       // is meaningless.
+                       assert(node->effect->effect_type_id() != "GammaExpansionEffect");
+
+                       AlphaType desired_type = ALPHA_PREMULTIPLIED;
+
+                       // GammaCompressionEffect is special; it needs postmultiplied alpha.
+                       if (node->effect->effect_type_id() == "GammaCompressionEffect") {
+                               assert(node->incoming_links.size() == 1);
+                               assert(node->incoming_links[0]->output_alpha_type == ALPHA_PREMULTIPLIED);
+                               desired_type = ALPHA_POSTMULTIPLIED;
+                       }
+
+                       // Go through each input that is not premultiplied alpha, and insert
+                       // a conversion before it.
+                       for (unsigned j = 0; j < node->incoming_links.size(); ++j) {
+                               Node *input = node->incoming_links[j];
+                               assert(input->output_alpha_type != ALPHA_INVALID);
+                               if (input->output_alpha_type == desired_type ||
+                                   input->output_alpha_type == ALPHA_BLANK) {
+                                       continue;
+                               }
+                               Node *conversion;
+                               if (desired_type == ALPHA_PREMULTIPLIED) {
+                                       conversion = add_node(new AlphaMultiplicationEffect());
+                               } else {
+                                       conversion = add_node(new AlphaDivisionEffect());
+                               }
+                               conversion->output_alpha_type = desired_type;
+                               replace_sender(input, conversion);
+                               connect_nodes(input, conversion);
+                       }
+
+                       // Re-sort topologically, and propagate the new information.
+                       propagate_gamma_and_color_space();
+                       propagate_alpha();
+                       
+                       found_any = true;
+                       break;
+               }
+       
+               char filename[256];
+               sprintf(filename, "step%u-alphafix-iter%u.dot", step, ++alpha_propagation_pass);
+               output_dot(filename);
+               assert(alpha_propagation_pass < 100);
+       } while (found_any);
+
+       for (unsigned i = 0; i < nodes.size(); ++i) {
+               Node *node = nodes[i];
+               if (node->disabled) {
+                       continue;
+               }
+               assert(node->output_alpha_type != ALPHA_INVALID);
+       }
+}
+
 // Make so that the output is in the desired color space.
 void EffectChain::fix_output_color_space()
 {
        Node *output = find_output_node();
        if (output->output_color_space != output_format.color_space) {
-               Node *conversion = add_node(new ColorSpaceConversionEffect());
-               conversion->effect->set_int("source_space", output->output_color_space);
-               conversion->effect->set_int("destination_space", output_format.color_space);
+               Node *conversion = add_node(new ColorspaceConversionEffect());
+               CHECK(conversion->effect->set_int("source_space", output->output_color_space));
+               CHECK(conversion->effect->set_int("destination_space", output_format.color_space));
                conversion->output_color_space = output_format.color_space;
                connect_nodes(output, conversion);
+               propagate_alpha();
+               propagate_gamma_and_color_space();
+       }
+}
+
+// Make so that the output is in the desired pre-/postmultiplication alpha state.
+void EffectChain::fix_output_alpha()
+{
+       Node *output = find_output_node();
+       assert(output->output_alpha_type != ALPHA_INVALID);
+       if (output->output_alpha_type == ALPHA_BLANK) {
+               // No alpha output, so we don't care.
+               return;
+       }
+       if (output->output_alpha_type == ALPHA_PREMULTIPLIED &&
+           output_alpha_format == OUTPUT_ALPHA_FORMAT_POSTMULTIPLIED) {
+               Node *conversion = add_node(new AlphaDivisionEffect());
+               connect_nodes(output, conversion);
+               propagate_alpha();
+               propagate_gamma_and_color_space();
+       }
+       if (output->output_alpha_type == ALPHA_POSTMULTIPLIED &&
+           output_alpha_format == OUTPUT_ALPHA_FORMAT_PREMULTIPLIED) {
+               Node *conversion = add_node(new AlphaMultiplicationEffect());
+               connect_nodes(output, conversion);
+               propagate_alpha();
+               propagate_gamma_and_color_space();
        }
 }
 
@@ -707,6 +1158,22 @@ bool EffectChain::node_needs_gamma_fix(Node *node)
        if (node->disabled) {
                return false;
        }
+
+       // Small hack since the output is not an explicit node:
+       // If we are the last node and our output is in the wrong
+       // space compared to EffectChain's output, we need to fix it.
+       // This will only take us to linear, but fix_output_gamma()
+       // will come and take us to the desired output gamma
+       // if it is needed.
+       //
+       // This needs to be before everything else, since it could
+       // even apply to inputs (if they are the only effect).
+       if (node->outgoing_links.empty() &&
+           node->output_gamma_curve != output_format.gamma_curve &&
+           node->output_gamma_curve != GAMMA_LINEAR) {
+               return true;
+       }
+
        if (node->effect->num_inputs() == 0) {
                return false;
        }
@@ -721,6 +1188,7 @@ bool EffectChain::node_needs_gamma_fix(Node *node)
                assert(node->incoming_links.size() == 1);
                return node->incoming_links[0]->output_gamma_curve != GAMMA_LINEAR;
        }
+
        return (node->effect->needs_linear_light() && node->output_gamma_curve != GAMMA_LINEAR);
 }
 
@@ -743,7 +1211,7 @@ void EffectChain::fix_internal_gamma_by_asking_inputs(unsigned step)
                        }
 
                        // See if all inputs can give us linear gamma. If not, leave it.
-                       std::vector<Node *> nonlinear_inputs;
+                       vector<Node *> nonlinear_inputs;
                        find_all_nonlinear_inputs(node, &nonlinear_inputs);
                        assert(!nonlinear_inputs.empty());
 
@@ -758,7 +1226,7 @@ void EffectChain::fix_internal_gamma_by_asking_inputs(unsigned step)
                        }
 
                        for (unsigned i = 0; i < nonlinear_inputs.size(); ++i) {
-                               nonlinear_inputs[i]->effect->set_int("output_linear_gamma", 1);
+                               CHECK(nonlinear_inputs[i]->effect->set_int("output_linear_gamma", 1));
                                nonlinear_inputs[i]->output_gamma_curve = GAMMA_LINEAR;
                        }
 
@@ -788,8 +1256,21 @@ void EffectChain::fix_internal_gamma_by_inserting_nodes(unsigned step)
                                continue;
                        }
 
-                       // Go through each input that is not linear gamma, and insert
-                       // a gamma conversion before it.
+                       // Special case: We could be an input and still be asked to
+                       // fix our gamma; if so, we should be the only node
+                       // (as node_needs_gamma_fix() would only return true in
+                       // for an input in that case). That means we should insert
+                       // a conversion node _after_ ourselves.
+                       if (node->incoming_links.empty()) {
+                               assert(node->outgoing_links.empty());
+                               Node *conversion = add_node(new GammaExpansionEffect());
+                               CHECK(conversion->effect->set_int("source_curve", node->output_gamma_curve));
+                               conversion->output_gamma_curve = GAMMA_LINEAR;
+                               connect_nodes(node, conversion);
+                       }
+
+                       // If not, go through each input that is not linear gamma,
+                       // and insert a gamma conversion after it.
                        for (unsigned j = 0; j < node->incoming_links.size(); ++j) {
                                Node *input = node->incoming_links[j];
                                assert(input->output_gamma_curve != GAMMA_INVALID);
@@ -797,12 +1278,14 @@ void EffectChain::fix_internal_gamma_by_inserting_nodes(unsigned step)
                                        continue;
                                }
                                Node *conversion = add_node(new GammaExpansionEffect());
-                               conversion->effect->set_int("source_curve", input->output_gamma_curve);
+                               CHECK(conversion->effect->set_int("source_curve", input->output_gamma_curve));
                                conversion->output_gamma_curve = GAMMA_LINEAR;
-                               insert_node_between(input, conversion, node);
+                               replace_sender(input, conversion);
+                               connect_nodes(input, conversion);
                        }
 
                        // Re-sort topologically, and propagate the new information.
+                       propagate_alpha();
                        propagate_gamma_and_color_space();
                        
                        found_any = true;
@@ -832,18 +1315,34 @@ void EffectChain::fix_output_gamma()
        Node *output = find_output_node();
        if (output->output_gamma_curve != output_format.gamma_curve) {
                Node *conversion = add_node(new GammaCompressionEffect());
-               conversion->effect->set_int("destination_curve", output_format.gamma_curve);
+               CHECK(conversion->effect->set_int("destination_curve", output_format.gamma_curve));
                conversion->output_gamma_curve = output_format.gamma_curve;
                connect_nodes(output, conversion);
        }
 }
+       
+// If the user has requested dither, add a DitherEffect right at the end
+// (after GammaCompressionEffect etc.). This needs to be done after everything else,
+// since dither is about the only effect that can _not_ be done in linear space.
+void EffectChain::add_dither_if_needed()
+{
+       if (num_dither_bits == 0) {
+               return;
+       }
+       Node *output = find_output_node();
+       Node *dither = add_node(new DitherEffect());
+       CHECK(dither->effect->set_int("num_bits", num_dither_bits));
+       connect_nodes(output, dither);
+
+       dither_effect = dither->effect;
+}
 
 // Find the output node. This is, simply, one that has no outgoing links.
 // If there are multiple ones, the graph is malformed (we do not support
 // multiple outputs right now).
 Node *EffectChain::find_output_node()
 {
-       std::vector<Node *> output_nodes;
+       vector<Node *> output_nodes;
        for (unsigned i = 0; i < nodes.size(); ++i) {
                Node *node = nodes[i];
                if (node->disabled) {
@@ -859,6 +1358,10 @@ Node *EffectChain::find_output_node()
 
 void EffectChain::finalize()
 {
+       // Save the current locale, and set it to C, so that we can output decimal
+       // numbers with printf and be sure to get them in the format mandated by GLSL.
+       char *saved_locale = setlocale(LC_NUMERIC, "C");
+
        // Output the graph as it is before we do any conversions on it.
        output_dot("step0-start.dot");
 
@@ -870,75 +1373,72 @@ void EffectChain::finalize()
        }
        output_dot("step1-rewritten.dot");
 
+       find_color_spaces_for_inputs();
+       output_dot("step2-input-colorspace.dot");
+
+       propagate_alpha();
+       output_dot("step3-propagated-alpha.dot");
+
        propagate_gamma_and_color_space();
-       output_dot("step2-propagated.dot");
+       output_dot("step4-propagated-all.dot");
 
        fix_internal_color_spaces();
+       fix_internal_alpha(6);
        fix_output_color_space();
-       output_dot("step4-output-colorspacefix.dot");
+       output_dot("step7-output-colorspacefix.dot");
+       fix_output_alpha();
+       output_dot("step8-output-alphafix.dot");
 
        // Note that we need to fix gamma after colorspace conversion,
        // because colorspace conversions might create needs for gamma conversions.
        // Also, we need to run an extra pass of fix_internal_gamma() after 
-       // fixing the output gamma, as we only have conversions to/from linear.
-       fix_internal_gamma_by_asking_inputs(5);
-       fix_internal_gamma_by_inserting_nodes(6);
+       // fixing the output gamma, as we only have conversions to/from linear,
+       // and fix_internal_alpha() since GammaCompressionEffect needs
+       // postmultiplied input.
+       fix_internal_gamma_by_asking_inputs(9);
+       fix_internal_gamma_by_inserting_nodes(10);
        fix_output_gamma();
-       output_dot("step7-output-gammafix.dot");
-       fix_internal_gamma_by_asking_inputs(8);
-       fix_internal_gamma_by_inserting_nodes(9);
+       output_dot("step11-output-gammafix.dot");
+       propagate_alpha();
+       output_dot("step12-output-alpha-propagated.dot");
+       fix_internal_alpha(13);
+       output_dot("step14-output-alpha-fixed.dot");
+       fix_internal_gamma_by_asking_inputs(15);
+       fix_internal_gamma_by_inserting_nodes(16);
+
+       output_dot("step17-before-dither.dot");
 
-       output_dot("step10-final.dot");
+       add_dither_if_needed();
+
+       output_dot("step18-final.dot");
        
        // Construct all needed GLSL programs, starting at the output.
        construct_glsl_programs(find_output_node());
 
-       // If we have more than one phase, we need intermediate render-to-texture.
-       // Construct an FBO, and then as many textures as we need.
-       // We choose the simplest option of having one texture per output,
-       // since otherwise this turns into an (albeit simple)
-       // register allocation problem.
-       if (phases.size() > 1) {
-               glGenFramebuffers(1, &fbo);
-
-               for (unsigned i = 0; i < phases.size() - 1; ++i) {
-                       inform_input_sizes(phases[i]);
-                       find_output_size(phases[i]);
-
-                       Node *output_node = phases[i]->effects.back();
-                       glGenTextures(1, &output_node->output_texture);
-                       check_error();
-                       glBindTexture(GL_TEXTURE_2D, output_node->output_texture);
-                       check_error();
-                       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
-                       check_error();
-                       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-                       check_error();
-                       glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16F_ARB, phases[i]->output_width, phases[i]->output_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
-                       check_error();
-
-                       output_node->output_texture_width = phases[i]->output_width;
-                       output_node->output_texture_height = phases[i]->output_height;
-               }
-               inform_input_sizes(phases.back());
-       }
-               
-       for (unsigned i = 0; i < inputs.size(); ++i) {
-               inputs[i]->finalize();
-       }
+       output_dot("step19-split-to-phases.dot");
 
        assert(phases[0]->inputs.empty());
        
        finalized = true;
+       setlocale(LC_NUMERIC, saved_locale);
 }
 
-void EffectChain::render_to_screen()
+void EffectChain::render_to_fbo(GLuint dest_fbo, unsigned width, unsigned height)
 {
        assert(finalized);
 
        // Save original viewport.
-       GLint viewport[4];
-       glGetIntegerv(GL_VIEWPORT, viewport);
+       GLuint x = 0, y = 0;
+       GLuint fbo = 0;
+
+       if (width == 0 && height == 0) {
+               GLint viewport[4];
+               glGetIntegerv(GL_VIEWPORT, viewport);
+               x = viewport[0];
+               y = viewport[1];
+               width = viewport[2];
+               height = viewport[3];
+       }
 
        // Basic state.
        glDisable(GL_BLEND);
@@ -948,53 +1448,39 @@ void EffectChain::render_to_screen()
        glDepthMask(GL_FALSE);
        check_error();
 
-       glMatrixMode(GL_PROJECTION);
-       glLoadIdentity();
-       glOrtho(0.0, 1.0, 0.0, 1.0, 0.0, 1.0);
-
-       glMatrixMode(GL_MODELVIEW);
-       glLoadIdentity();
-
        if (phases.size() > 1) {
+               glGenFramebuffers(1, &fbo);
+               check_error();
                glBindFramebuffer(GL_FRAMEBUFFER, fbo);
                check_error();
        }
 
-       std::set<Node *> generated_mipmaps;
+       set<Node *> generated_mipmaps;
+
+       // We choose the simplest option of having one texture per output,
+       // since otherwise this turns into an (albeit simple) register allocation problem.
+       map<Phase *, GLuint> output_textures;
 
        for (unsigned phase = 0; phase < phases.size(); ++phase) {
-               // See if the requested output size has changed. If so, we need to recreate
-               // the texture (and before we start setting up inputs).
+               // Find a texture for this phase.
                inform_input_sizes(phases[phase]);
                if (phase != phases.size() - 1) {
                        find_output_size(phases[phase]);
 
-                       Node *output_node = phases[phase]->effects.back();
-
-                       if (output_node->output_texture_width != phases[phase]->output_width ||
-                           output_node->output_texture_height != phases[phase]->output_height) {
-                               glActiveTexture(GL_TEXTURE0);
-                               check_error();
-                               glBindTexture(GL_TEXTURE_2D, output_node->output_texture);
-                               check_error();
-                               glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16F_ARB, phases[phase]->output_width, phases[phase]->output_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
-                               check_error();
-                               glBindTexture(GL_TEXTURE_2D, 0);
-                               check_error();
-
-                               output_node->output_texture_width = phases[phase]->output_width;
-                               output_node->output_texture_height = phases[phase]->output_height;
-                       }
+                       GLuint tex_num = resource_pool->create_2d_texture(GL_RGBA16F_ARB, phases[phase]->output_width, phases[phase]->output_height);
+                       output_textures.insert(make_pair(phases[phase], tex_num));
                }
 
-               glUseProgram(phases[phase]->glsl_program_num);
+               const GLuint glsl_program_num = phases[phase]->glsl_program_num;
+               check_error();
+               glUseProgram(glsl_program_num);
                check_error();
 
                // Set up RTT inputs for this phase.
                for (unsigned sampler = 0; sampler < phases[phase]->inputs.size(); ++sampler) {
                        glActiveTexture(GL_TEXTURE0 + sampler);
                        Node *input = phases[phase]->inputs[sampler];
-                       glBindTexture(GL_TEXTURE_2D, input->output_texture);
+                       glBindTexture(GL_TEXTURE_2D, output_textures[input->phase]);
                        check_error();
                        if (phases[phase]->input_needs_mipmaps) {
                                if (generated_mipmaps.count(input) == 0) {
@@ -1008,27 +1494,38 @@ void EffectChain::render_to_screen()
                                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
                                check_error();
                        }
+                       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+                       check_error();
+                       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+                       check_error();
 
-                       std::string texture_name = std::string("tex_") + input->effect_id;
-                       glUniform1i(glGetUniformLocation(phases[phase]->glsl_program_num, texture_name.c_str()), sampler);
+                       string texture_name = string("tex_") + phases[phase]->effect_ids[input];
+                       glUniform1i(glGetUniformLocation(glsl_program_num, texture_name.c_str()), sampler);
                        check_error();
                }
 
                // And now the output.
                if (phase == phases.size() - 1) {
-                       // Last phase goes directly to the screen.
-                       glBindFramebuffer(GL_FRAMEBUFFER, 0);
+                       // Last phase goes to the output the user specified.
+                       glBindFramebuffer(GL_FRAMEBUFFER, dest_fbo);
                        check_error();
-                       glViewport(viewport[0], viewport[1], viewport[2], viewport[3]);
+                       GLenum status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
+                       assert(status == GL_FRAMEBUFFER_COMPLETE);
+                       glViewport(x, y, width, height);
+                       if (dither_effect != NULL) {
+                               CHECK(dither_effect->set_int("output_width", width));
+                               CHECK(dither_effect->set_int("output_height", height));
+                       }
                } else {
-                       Node *output_node = phases[phase]->effects.back();
                        glFramebufferTexture2D(
                                GL_FRAMEBUFFER,
                                GL_COLOR_ATTACHMENT0,
                                GL_TEXTURE_2D,
-                               output_node->output_texture,
+                               output_textures[phases[phase]],
                                0);
                        check_error();
+                       GLenum status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
+                       assert(status == GL_FRAMEBUFFER_COMPLETE);
                        glViewport(0, 0, phases[phase]->output_width, phases[phase]->output_height);
                }
 
@@ -1036,31 +1533,58 @@ void EffectChain::render_to_screen()
                unsigned sampler_num = phases[phase]->inputs.size();
                for (unsigned i = 0; i < phases[phase]->effects.size(); ++i) {
                        Node *node = phases[phase]->effects[i];
-                       node->effect->set_gl_state(phases[phase]->glsl_program_num, node->effect_id, &sampler_num);
+                       node->effect->set_gl_state(glsl_program_num, phases[phase]->effect_ids[node], &sampler_num);
                        check_error();
                }
 
                // Now draw!
-               glBegin(GL_QUADS);
-
-               glTexCoord2f(0.0f, 0.0f);
-               glVertex2f(0.0f, 0.0f);
+               float vertices[] = {
+                       0.0f, 1.0f,
+                       0.0f, 0.0f,
+                       1.0f, 1.0f,
+                       1.0f, 0.0f
+               };
+
+               GLuint vao;
+               glGenVertexArrays(1, &vao);
+               check_error();
+               glBindVertexArray(vao);
+               check_error();
 
-               glTexCoord2f(1.0f, 0.0f);
-               glVertex2f(1.0f, 0.0f);
+               GLuint position_vbo = fill_vertex_attribute(glsl_program_num, "position", 2, GL_FLOAT, sizeof(vertices), vertices);
+               GLuint texcoord_vbo = fill_vertex_attribute(glsl_program_num, "texcoord", 2, GL_FLOAT, sizeof(vertices), vertices);  // Same as vertices.
 
-               glTexCoord2f(1.0f, 1.0f);
-               glVertex2f(1.0f, 1.0f);
+               glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+               check_error();
 
-               glTexCoord2f(0.0f, 1.0f);
-               glVertex2f(0.0f, 1.0f);
+               cleanup_vertex_attribute(glsl_program_num, "position", position_vbo);
+               cleanup_vertex_attribute(glsl_program_num, "texcoord", texcoord_vbo);
 
-               glEnd();
+               glUseProgram(0);
                check_error();
 
                for (unsigned i = 0; i < phases[phase]->effects.size(); ++i) {
                        Node *node = phases[phase]->effects[i];
                        node->effect->clear_gl_state();
                }
+
+               glDeleteVertexArrays(1, &vao);
+               check_error();
+       }
+
+       for (map<Phase *, GLuint>::const_iterator texture_it = output_textures.begin();
+            texture_it != output_textures.end();
+            ++texture_it) {
+               resource_pool->release_2d_texture(texture_it->second);
+       }
+
+       glBindFramebuffer(GL_FRAMEBUFFER, 0);
+       check_error();
+
+       if (fbo != 0) {
+               glDeleteFramebuffers(1, &fbo);
+               check_error();
        }
 }
+
+}  // namespace movit