You could use the Toolkit, no need for ImageIO
Image image = Toolkit.getDefaultToolkit().getImage(file.getAbsolutePath());
int width = image.getWidth(null);
int height = image.getHeight(null);
If you don't want to handle the loading of the image do
ImageIcon imageIcon = new ImageIcon(file.getAbsolutePath());
int height = imageIcon.getIconHeight();
int width = imageIcon.getIconWidth();