Canvas, Palettes, Bitmap updates

src/app/gfx/bitmap.cc

@@ -348,8 +348,8 @@ void Bitmap::ApplyPalette(const SNESPalette &palette) {
 
 void Bitmap::ApplyPaletteWithTransparent(const SNESPalette &palette,
                                          int index) {
-  palette_ = palette;
   auto start_index = index * 7;
+  palette_ = palette.sub_palette(start_index, start_index + 7);
   std::vector<ImVec4> colors;
   colors.push_back(ImVec4(0, 0, 0, 0));
   for (int i = start_index; i < start_index + 7; ++i) {

src/app/gfx/bitmap.h

@@ -81,6 +81,40 @@ class Bitmap {
     }
   }
 
+  Uint8 ConvertImVec4ToIndex8(const ImVec4 &color, SDL_Surface *surface) {
+    if (surface->format->format != SDL_PIXELFORMAT_INDEX8) {
+      throw std::runtime_error(
+          "Surface is not in SDL_PIXELFORMAT_INDEX8 format.");
+    }
+
+    // Convert ImVec4 (RGBA) to SDL_Color (RGBA)
+    SDL_Color sdl_color;
+    sdl_color.r = static_cast<Uint8>(color.x * 255);
+    sdl_color.g = static_cast<Uint8>(color.y * 255);
+    sdl_color.b = static_cast<Uint8>(color.z * 255);
+    sdl_color.a = static_cast<Uint8>(color.w * 255);
+
+    // Map SDL_Color to the nearest color index in the surface's palette
+    return SDL_MapRGB(surface->format, sdl_color.r, sdl_color.g, sdl_color.b);
+  }
+
+  void WriteColor(int position, const ImVec4 &color) {
+    // Convert ImVec4 (RGBA) to SDL_Color (RGBA)
+    SDL_Color sdl_color;
+    sdl_color.r = static_cast<Uint8>(color.x * 255);
+    sdl_color.g = static_cast<Uint8>(color.y * 255);
+    sdl_color.b = static_cast<Uint8>(color.z * 255);
+    sdl_color.a = static_cast<Uint8>(color.w * 255);
+
+    // Map SDL_Color to the nearest color index in the surface's palette
+    Uint8 index =
+        SDL_MapRGB(surface_->format, sdl_color.r, sdl_color.g, sdl_color.b);
+
+    // Write the color index to the pixel data
+    this->pixel_data_[position] = index;
+    modified_ = true;
+  }
+
   void Cleanup() {
     // Reset texture_
     if (texture_) {
@@ -106,6 +140,15 @@ class Bitmap {
     palette_.Clear();
   }
 
+  auto sdl_palette() {
+    if (surface_ == nullptr) {
+      throw std::runtime_error("Surface is null.");
+    }
+    return surface_->format->palette;
+  }
+  auto palette() const { return palette_; }
+  auto palette_size() const { return palette_.size(); }
+
   int width() const { return width_; }
   int height() const { return height_; }
   auto depth() const { return depth_; }

src/app/gfx/snes_palette.h

@@ -187,6 +187,14 @@ class SNESPalette {
     colors[i].SetModified(true);
   }
 
+  SNESPalette sub_palette(int start, int end) const {
+    SNESPalette pal;
+    for (int i = start; i < end; i++) {
+      pal.AddColor(colors[i]);
+    }
+    return pal;
+  }
+
  private:
   int size_ = 0;                 /**< The size of the palette. */
   std::vector<SNESColor> colors; /**< The colors in the palette. */