You can create a new image, a BufferedImage with the TookitImage.
Image toolkitImage = img.getScaledInstance(getWidth(), getHeight(),
Image.SCALE_SMOOTH);
int width = toolkitImage.getWidth(null);
int height = toolkitImage.getHeight(null);
// width and height are of the toolkit image
BufferedImage newImage = new BufferedImage(width, height,
BufferedImage.TYPE_INT_ARGB);
Graphics g = newImage.getGraphics();
g.drawImage(toolkitImage, 0, 0, null);
g.dispose();
// now use your new BufferedImage