Adding two BufferedImages without painting on screen?

Question

Hi all,
I am trying to combine two (or more) BufferedImages into onee BufferedImage, such that the result is a BufferedImage that represents all the images laid out side-by-side. (If I get a result for two images I can work out multiple images by myself)
This would be quite simple if I were interested in displaying the images, as I could extend a JPanel or JLabel or whatever, and modify the paint() or paintComponent() method to paint out all the BufferedImages. I could then use this to create a new BufferedImage if I wanted.
However, I want to be able to create a BufferedImage (or a Byte Array) without ever needing to paint the images on the screen. I need to be able to save the resulting BufferedImage/byet[] without needing to pop up a little panel to paint on.
Is there any way to do this?
Thanks!
Sam

Answer 1

Here is my implementation along the lines suggested. I assume all images are the same size. I have only actually tested this code for the case where rows = columns.
/** Combines an list of images into a new bigger buffered image.
    * The images in the list should be in 'across then down' order (like a regular GridLayout).
    * We assume that all the images in the array
    * are the same size as the first one.
    * If rows * columns is bigger than the size of
    * the array then some of the resulting image will remain black. 
    * If rows * columns is less, then
    * some of the images in the list are unused.
   public static BufferedImage tileBufferedImages(List<BufferedImage> bis, int rows, int columns)
      if (bis==null || bis.size()==0) throw new IllegalArgumentException("images must be provided");
      int height = bis.get(0).getHeight();
      int width = bis.get(0).getWidth();
      BufferedImage combo = new BufferedImage(width * columns,
               height * rows, BufferedImage.TYPE_INT_ARGB);
      Graphics2D g2 = combo.createGraphics();
      int i=0;
      for (int r= 0 ; r < rows; ++r) for (int c = 0; c < columns; ++c)
         if (i< bis.size())
            g2.drawImage(bis.get(i), c*width, r*height, null);
         ++i;
      g2.dispose();
      return combo;
   Edited by: RobWall on Nov 27, 2007 12:39 AM
Edited by: RobWall on Nov 27, 2007 8:37 PM