Board game -alternate way to draw

Question

Thanks for reading,
im relatively new to game devpmt, i am making a board game similar to pool.
the board background is a JPanel on which a fixed image is drawn .i want to make a ball moving on it.The ball's image is loaded from a file .since the image is rectangular in boundary,ball when drawn on the board,displays the rectangular boundaries around it.
is there any way to overcome this problem,
all the drawings of board_backround_image and ball_image takesplace when the paintComponent() of the boardpanel is called.
Any suggestions would b great helpful.....

Answer 1

If you are reading from gif or png, make the background of the source image transparent. Otherwise, color the background with some unused palette color, search through the pixels after loading, and replace those pixels with transparent ones.
If using jpg or some other lossy compression scheme, you'll not only need to have a transparency marker, but it will not always have the same RGB to compare with. Here's a quick snippet that will covert a particular color in an image to transparent pixels. The fuzziness variable is how far the red, green, and blue channels may be to still be considered marked as transparent.
public BufferedImage transparify(Image sourceImage, Color replaceColor, int fuzziness)
   int imageWidth = sourceImage.getWidth(null);
   int imageHeight = sourceImage.getHeight(null);
   // ensure we are using a ARGB BufferedImage
   BufferedImage returnImage = new BufferedImage(imageWidth,imageHeight, BufferedImage.TYPE_INT_ARGB);
   Graphics imageG = returnImage.getGraphics();
   imageG.drawImage(sourceImage, 0, 0, null);
   imageG.dispose();
   // extract pixel data
   int[] pixels = new int[imageWidth * imageHeight];
   returnImage.getRGB(0, 0, imageWidth, imageHeight, pixels, 0, imageWidth);
   int transRed   = replaceColor.getRed();
   int transGreen = replaceColor.getGreen();
   int transBlue  = replaceColor.getBlue();
   for (int pixIndex = 0; pixIndex < pixels.length; pixIndex++) {
      // sum the difference of this pixel with the transparency marker
      int diffRed   = transRed   - ((pixels[pixIndex] >> 16) & 0xFF);
      int diffGreen = transGreen - ((pixels[pixIndex] >> 8) & 0xFF);
      int diffBlue  = transBlue -  (pixels[pixIndex] & 0xFF);
      // if close to the marker, set pixel to transparent
      boolean closeEnough = (diffRed >= 0 ? diffRed : -diffRed) <= fuzziness &&     
                      (diffGreen >= 0 ? diffGreen : -diffGreen) <= fuzziness &&  
                      (diffBlue >= 0 ? diffBlue : -diffBlue) <= fuzziness;
      if (closeEnough) {
         pixels[pixIndex] = 0; // 0 alpha makes transparent
   returnImage.setRGB(0, 0, imageWidth, imageHeight, pixels, 0, imageWidth);
   return returnImage;
}