transparent pngs/gifs

OpenGL Development JOGL Development
#1

How come when I load png or gif files as textures, the transparency dissapears?

this is my texture loader method:



public static int loadTexture(GL gl, String filename) throws TextureException
      {
            if(TextureManager.loadedTextures.containsKey(filename))
                  return ((Integer)TextureManager.loadedTextures.get(filename)).intValue();

            BufferedImage img = null;
            
            // Load the image
            try      {
                  img = ImageIO.read(new File(filename));
            } catch (Exception e) {
                  throw new TextureException("TextureException - " + filename + " - " +  e.getMessage());
            }
            
            ByteBuffer dest = null;

          int[] data = new int[img.getWidth()*img.getHeight()];

          for(int y = 0; y<img.getHeight(); ++y)
          {
                int _y = y*img.getWidth();
                for(int x = 0; x<img.getWidth(); ++x)
                {
                      data[_y+x] = img.getRGB(x,y);
                }
          }
          
          // Convert from bgra to rgba pixel format
          bgra2rgba(data);
            dest = ByteBuffer.allocateDirect(data.length * BufferUtils.SIZEOF_INT);
            dest.order(ByteOrder.nativeOrder());
            dest.asIntBuffer().put(data, 0, data.length);
            
            int[] id = new int[1];
            // Generate a texture and bind it
            gl.glGenTextures(1, id);
            gl.glBindTexture(gl.GL_TEXTURE_2D, id[0]);
            // Set texture filters to linear interpolation
            gl.glTexParameteri(gl.GL_TEXTURE_2D,gl.GL_TEXTURE_MIN_FILTER,gl.GL_LINEAR);
            gl.glTexParameteri(gl.GL_TEXTURE_2D,gl.GL_TEXTURE_MAG_FILTER,gl.GL_LINEAR);
            // Upload the image to video memory
            gl.glTexImage2D(gl.GL_TEXTURE_2D, 0, gl.GL_RGBA, img.getWidth(), img.getHeight(), 0, gl.GL_RGBA, gl.GL_UNSIGNED_BYTE, dest);
            
            // Store the image id
            TextureManager.loadedTextures.put(filename, new Integer(id[0]));
            
            return id[0];
      }
      
      //converts picture buffers from bgra to rgba
      protected static void bgra2rgba(int[] argb)
      {
            for(int v = 0; v<argb.length; ++v)
            {
                  int c = (argb[v] & 0xFF00FF00);
                  int r = (argb[v] & 0x00FF0000) >> 16;
                  int b = (argb[v] & 0x000000FF) << 16;
                  int finalc = c|r|b;
                  int rgb = ((finalc & 0x00FFFFFF) == 0x00FF00FF)?(finalc & 0x00FFFFFF):finalc;
                  argb[v] = rgb;
            }      
      }

thanx a lot for any help

#2

IIRC to make opengl take the alpha values into account you have to either enable alpha blending or alpha testing.
For alpha blending you need to call

glEnable(GL_BLEND)
glBlendFunc(...);

For the alpha testing you need to call

glEnable(GL_ALPHA_TEST);
glAlphaFunc(...);

Alpha testing is faster than blending but doesn’t look as nice.