java - Out of memory problem saving large BufferedImage

Question

I have a problem saving large (f.e. 12 000 x 9 000 ) images.

I'm developing a graphical editing software ( something like simple Photoshop ) and The user obviously has to have to ability to save the image.

Lets say I would like to save the image as .png. Does JAVA always need to use the BufferedImage for saving drawn stuff ?

I know the equation for size of the image is: Xsize * Ysize * 4 ( red, green, blue, alpha ) So in this case we get over 400 MB.

I know I could save the image in parts ( tiles ) but the user would have to merge them somehow anyway.

Is there any other way to save such a large image without using the BufferedImage ?

Code for saving the image:

 public static void SavePanel() {

    BufferedImage image = null;
    image =  new BufferedImage(
            (int) (Main.scale * sizeX ),
            (int) (Main.scale * sizeY ),
            BufferedImage.TYPE_INT_RGB);

    g2 = image.createGraphics();
    panel.paint(g2);


    try {
        ImageIO.write(image, "png", new File(FactoryDialog.ProjectNameTxt.getText() + ".png"));
    } catch (IOException e) {
    }


}

Thank you in advance !

Answer 1

The ImageIO.write(..) methods accept an RenderedImage, not just a BufferedImage. I successfully exploited this fact some time ago to write out really large images. Generally, the writer implementations write out the image sequentially, and ask the RenderedImage only for the pieces they currently need.

From looking at your code, I think it should be possible to hack a RenderedImage implementation which takes your panel in it's constructor and can be passed to ImageIO for writing. During the process, ImageIO will request data from your image. You can then use the panel to create the requested pieces (Raster contents) on the fly. This way, the whole image does not have to be stored in memory at any point. A starting point for this approach is

public class PanelImage implements RenderedImage {

   private final Panel panel;

   public PanelImage(Panel panel) {
      this.panel = panel;
   }

   /* implement all the missing methods, don't be afraid, most are trivial */

}

Obviously, you should also check if your panel doesn't suffer from the same problem as the BufferedImage. Depending on the nature of you application, you'll have to hold the image in memory at least once anyway (modulo using tiles). But this way you can at least avoid the duplication.