e594. reading an image or icon from a file.txt

这里面包含了一百多个JAVA源文件

See also e595 Drawing an Image. 
    // This call returns immediately and pixels are loaded in the background
    Image image = Toolkit.getDefaultToolkit().getImage("image.gif");
    int width = image.getWidth(null);
    int height = image.getHeight(null);
    
    if (width >= 0) {
        // The image has been fully loaded
    } else {
        // The image has not been fully loaded
    }
    
    
    // This method ensures that all pixels have been loaded before returning
    image = new ImageIcon("image.gif").getImage();
    
    // Get the dimensions of the image; these will be non-negative
    width = image.getWidth(null);
    height = image.getHeight(null);