decompiler: add texture merging feature

decompiler/data/TextureDB.cpp

@@ -99,6 +99,36 @@ void TextureDB::add_index_texture(u32 tpage,
   }
 }
 
+void TextureDB::merge_textures(const fs::path& base_path) {
+  for (auto& tex : textures) {
+    fs::path full_path = base_path / tpage_names.at(tex.second.page) / (tex.second.name + ".png");
+    if (fs::exists(full_path)) {
+      lg::info("Merging {}", full_path.string().c_str());
+      int w, h;
+      auto merge_data = stbi_load(full_path.string().c_str(), &w, &h, 0, 4);  // rgba channels
+      if (!merge_data) {
+        lg::warn("failed to load PNG file: {}", full_path.string().c_str());
+        continue;
+      } else if (w != tex.second.w || h != tex.second.h) {
+        lg::warn("merge texture does not match the same dimensions: {}, {} != {} || {} != {}",
+                 full_path.string().c_str(), w, tex.second.w, h, tex.second.h);
+        stbi_image_free(merge_data);
+        continue;
+      }
+      // Merge any non-transparent pixels into the existing texture
+      for (int i = 0; i < w * h * 4; i += 4) {
+        const auto merge_pixel_a = merge_data[i + 3];
+        if (merge_pixel_a != 0) {
+          u32 merge_pixel;
+          memcpy(&merge_pixel, &merge_data[i], sizeof(u32));
+          tex.second.rgba_bytes.at(i / 4) = merge_pixel;
+        }
+      }
+      stbi_image_free(merge_data);
+    }
+  }
+}
+
 void TextureDB::replace_textures(const fs::path& path) {
   fs::path base_path(path);
   for (auto& tex : textures) {

decompiler/data/TextureDB.h

@@ -55,6 +55,7 @@ struct TextureDB {
                          const std::string& tpage_name,
                          const std::vector<std::string>& level_names);
 
+  void merge_textures(const fs::path& base_path);
   void replace_textures(const fs::path& path);
 
   std::string generate_texture_dest_adjustment_table() const;

decompiler/extractor/main.cpp

@@ -172,6 +172,15 @@ void decompile(const fs::path& iso_data_path, const std::string& data_subfolder)
   file_util::create_dir_if_needed(textures_out);
   file_util::write_text_file(textures_out / "tpage-dir.txt",
                              db.process_tpages(tex_db, textures_out, config));
+
+  // texture merges
+  // TODO - put all this stuff in somewhere common
+  auto texture_merge_path = file_util::get_jak_project_dir() / "game" / "assets" /
+                            game_version_names[config.game_version] / "texture_merges";
+  if (fs::exists(texture_merge_path)) {
+    tex_db.merge_textures(texture_merge_path);
+  }
+
   // texture replacements
   auto replacements_path = file_util::get_jak_project_dir() / "texture_replacements";
   if (fs::exists(replacements_path)) {

decompiler/main.cpp

@@ -298,6 +298,13 @@ int main(int argc, char** argv) {
 
   mem_log("After textures: {} MB", get_peak_rss() / (1024 * 1024));
 
+  // Merge textures before replacing them, in other words, replacements take priority
+  auto texture_merge_path = file_util::get_jak_project_dir() / "game" / "assets" /
+                            game_version_names[config.game_version] / "texture_merges";
+  if (fs::exists(texture_merge_path)) {
+    tex_db.merge_textures(texture_merge_path);
+  }
+
   auto replacements_path = file_util::get_jak_project_dir() / "texture_replacements";
   if (fs::exists(replacements_path)) {
     tex_db.replace_textures(replacements_path);