The Java Developers Almanac 1.4

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e666. Creating a Buffered Image

A buffered image is a type of image whose pixels can be modified. For example, you can draw on a buffered image and then draw the resulting buffered image on the screen or save it to a file. A buffered image supports many formats for storing pixels. Although a buffered image of any format can be drawn on the screen, it is best to choose a format that is the most compatible with the screen to allow efficient drawing. This example demonstrates several ways of creating a buffered image.

If the buffered image will not be drawn, it can simply be constructed with a specific format; TYPE_INT_RGB and TYPE_INT_ARGB are typically used. See BufferedImage for a list of available formats.

    int width = 100;
    int height = 100;
    
    // Create buffered image that does not support transparency
    BufferedImage bimage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
    
    // Create a buffered image that supports transparency
    bimage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);

These examples create buffered images that are compatible with the screen:

    GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
    GraphicsDevice gs = ge.getDefaultScreenDevice();
    GraphicsConfiguration gc = gs.getDefaultConfiguration();
    
    // Create an image that does not support transparency
    bimage = gc.createCompatibleImage(width, height, Transparency.OPAQUE);
    
    // Create an image that supports transparent pixels
    bimage = gc.createCompatibleImage(width, height, Transparency.BITMASK);
    
    // Create an image that supports arbitrary levels of transparency
    bimage = gc.createCompatibleImage(width, height, Transparency.TRANSLUCENT);

A screen compatible buffered image can also be created from a graphics context:

    public void paint(Graphics g) {
        Graphics2D g2d = (Graphics2D)g;
        int width = 100;
        int height = 100;
    
        // Create an image that does not support transparency
        BufferedImage bimage = g2d.getDeviceConfiguration().createCompatibleImage(
            width, height, Transparency.OPAQUE);
    
        // Create an image that supports transparent pixels
        bimage = g2d.getDeviceConfiguration().createCompatibleImage(
            width, height, Transparency.BITMASK);
    
        // Create an image that supports arbitrary levels of transparency
        bimage = g2d.getDeviceConfiguration().createCompatibleImage(
            width, height, Transparency.TRANSLUCENT);
    }

One last way of creating a buffered image is using Component.createImage(). This method can be used only if the component is visible on the screen. Also, this method returns buffered images that do not support transparent pixels.

    BufferedImage bimage = (BufferedImage)component.createImage(width, height);
    if (bimage == null) {
        // The component is not visible on the screen
    }