// tested on this image http://www.goabroad.com/blog/wp-content/uploads/2012/10/GACoverPhotoContest.jpg

int pixels[][] = convertTo2DWithoutUsingGetRGB(image);

boolean withAlpha = false; // if you need the alpha channel change this to true
String imgFormat = "jpg";  // if you need the alpha channel change this to png
String imgPath   = "myImage." + imgFormat;

BufferedImage newImg = getImage(pixels, withAlpha);

ImageIO.write(newImg, imgFormat, new File(imgPath));

private static BufferedImage getImage(int[][] pixels, final boolean withAlpha)
{
  // Assuming pixels was taken from convertTo2DWithoutUsingGetRGB
  // i.e. img.length == pixels.length and img.width == pixels[x].length
  BufferedImage img = new BufferedImage(pixels[0].length, pixels.length, withAlpha ? BufferedImage.TYPE_4BYTE_ABGR : BufferedImage.TYPE_3BYTE_BGR);
  for (int y = 0; y < pixels.length; y++)
  {
     for (int x = 0; x < pixels[y].length; x++)
     {
        if (withAlpha)
           img.setRGB(x, y, pixels[y][x]);
        else {
           int pixel = pixels[y][x];
           int alpha = (pixel >> 24 & 0xff);
           int red   = (pixel >> 16 & 0xff);
           int green = (pixel >> 8 & 0xff);
           int blue  = (pixel & 0xff);
           int rgb = (red << 16) | (green << 8) | blue;
           img.setRGB(x, y, rgb);
        }
     }
  }
  return img;
}