some changes for alpha channel support (still doesn't work :( )

src/common/FBBackendSDL2.hxx

@@ -111,6 +111,11 @@ class FBBackendSDL2 : public FBBackend
     inline uInt32 mapRGB(uInt8 r, uInt8 g, uInt8 b) const override
       { return SDL_MapRGB(myPixelFormat, r, g, b); }
 
+    inline uInt32 mapRGBA(uInt8 r, uInt8 g, uInt8 b, uInt8 a) const override
+    {
+      return SDL_MapRGBA(myPixelFormat, r, g, b, a);
+    }
+
     /**
       This method is called to get a copy of the specified ARGB data from the
       viewable FrameBuffer area.  Note that this isn't the same as any

src/common/PNGLibrary.cxx

@@ -40,6 +40,7 @@ void PNGLibrary::loadImage(const string& filename, FBSurface& surface, VariantLi
   png_infop info_ptr{nullptr};
   png_uint_32 iwidth{0}, iheight{0};
   int bit_depth{0}, color_type{0}, interlace_type{0};
+  bool hasAlpha = false;
 
   const auto loadImageERROR = [&](string_view s) {
     if(png_ptr)
@@ -80,7 +81,8 @@ void PNGLibrary::loadImage(const string& filename, FBSurface& surface, VariantLi
   // Only normal RBG(A) images are supported (without the alpha channel)
   if(color_type == PNG_COLOR_TYPE_RGBA)
   {
-    png_set_strip_alpha(png_ptr);
+    hasAlpha = true;
+    //png_set_strip_alpha(png_ptr);
   }
   else if(color_type == PNG_COLOR_TYPE_GRAY || color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
   {
@@ -96,7 +98,7 @@ void PNGLibrary::loadImage(const string& filename, FBSurface& surface, VariantLi
   }
 
   // Create/initialize storage area for the current image
-  if(!allocateStorage(iwidth, iheight))
+  if(!allocateStorage(iwidth, iheight, hasAlpha))
     loadImageERROR("Not enough memory to read PNG image");
 
   // The PNG read function expects an array of rows, not a single 1-D array
@@ -113,7 +115,7 @@ void PNGLibrary::loadImage(const string& filename, FBSurface& surface, VariantLi
   readMetaData(png_ptr, info_ptr, metaData);
 
   // Load image into the surface, setting the correct dimensions
-  loadImagetoSurface(surface);
+  loadImagetoSurface(surface, hasAlpha);
 
   // Cleanup
   if(png_ptr)
@@ -381,10 +383,10 @@ void PNGLibrary::takeSnapshot(uInt32 number)
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-bool PNGLibrary::allocateStorage(size_t width, size_t height)
+bool PNGLibrary::allocateStorage(size_t width, size_t height, bool hasAlpha)
 {
   // Create space for the entire image (3 bytes per pixel in RGB format)
-  const size_t req_buffer_size = width * height * 3;
+  const size_t req_buffer_size = width * height * (hasAlpha ? 4 : 3);
   if(req_buffer_size > ReadInfo.buffer.capacity())
     ReadInfo.buffer.reserve(req_buffer_size * 1.5);
 
@@ -394,13 +396,13 @@ bool PNGLibrary::allocateStorage(size_t width, size_t height)
 
   ReadInfo.width  = static_cast<png_uint_32>(width);
   ReadInfo.height = static_cast<png_uint_32>(height);
-  ReadInfo.pitch  = static_cast<png_uint_32>(width * 3);
+  ReadInfo.pitch  = static_cast<png_uint_32>(width * (hasAlpha ? 4 : 3));
 
   return true;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void PNGLibrary::loadImagetoSurface(FBSurface& surface)
+void PNGLibrary::loadImagetoSurface(FBSurface& surface, bool hasAlpha)
 {
   // First determine if we need to resize the surface
   const uInt32 iw = ReadInfo.width, ih = ReadInfo.height;
@@ -423,6 +425,10 @@ void PNGLibrary::loadImagetoSurface(FBSurface& surface)
   {
     const uInt8* i_ptr = i_buf;
     uInt32* s_ptr = s_buf;
+    if(hasAlpha)
+      for(uInt32 icol = 0; icol < ReadInfo.width; ++icol, i_ptr += 4)
+        *s_ptr++ = fb.mapRGBA(*i_ptr, *(i_ptr+1), *(i_ptr+2), 85/* *(i_ptr+3)*/);
+    else
       for(uInt32 icol = 0; icol < ReadInfo.width; ++icol, i_ptr += 3)
         *s_ptr++ = fb.mapRGB(*i_ptr, *(i_ptr+1), *(i_ptr+2));
   }

src/common/PNGLibrary.hxx

@@ -153,7 +153,7 @@ class PNGLibrary
       @param width   The width of the PNG image
       @param height  The height of the PNG image
     */
-    static bool allocateStorage(size_t width, size_t height);
+    static bool allocateStorage(size_t width, size_t height, bool hasAlpha);
 
     /** The actual method which saves a PNG image.
 
@@ -173,7 +173,7 @@ class PNGLibrary
 
       @param surface  The FBSurface into which to place the PNG data
     */
-    void loadImagetoSurface(FBSurface& surface);
+    void loadImagetoSurface(FBSurface& surface, bool hasAlpha);
 
     /**
       Write PNG tEXt chunks to the image.

src/emucore/FBBackend.hxx

@@ -137,6 +137,15 @@ class FBBackend
     */
     virtual uInt32 mapRGB(uInt8 r, uInt8 g, uInt8 b) const = 0;
 
+    /**
+      This method is called to map a given R/G/B triple to the screen palette.
+
+      @param r  The red component of the color.
+      @param g  The green component of the color.
+      @param b  The blue component of the color.
+    */
+    virtual uInt32 mapRGBA(uInt8 r, uInt8 g, uInt8 b, uInt8 a) const = 0;
+
     /**
       This method is called to get the specified ARGB data from the viewable
       FrameBuffer area.  Note that this isn't the same as any internal

src/emucore/FrameBuffer.cxx

@@ -1320,8 +1320,8 @@ FBInitStatus FrameBuffer::applyVideoMode()
       const string& path = myOSystem.snapshotLoadDir().getPath();
 
       //loadBezel(path + "Atari-2600.png");
-      //loadBezel(path + "Combat.png");
+      loadBezel(path + "Combat (USA).png");
-      loadBezel(path + "Asteroids (USA).png");
+      //loadBezel(path + "Asteroids (USA).png");
     }
 
     resetSurfaces();

src/emucore/FrameBuffer.hxx

@@ -360,6 +360,17 @@ class FrameBuffer
       return myBackend->mapRGB(r, g, b);
     }
 
+    /**
+    This method is called to map a given R/G/B triple to the screen palette.
+
+    @param r  The red component of the color.
+    @param g  The green component of the color.
+    @param b  The blue component of the color.
+    */
+    uInt32 mapRGBA(uInt8 r, uInt8 g, uInt8 b, uInt8 a) const {
+      return myBackend->mapRGBA(r, g, b, a);
+    }
+
     /**
       This method is called to get the specified ARGB data from the viewable
       FrameBuffer area.  Note that this isn't the same as any internal