Example usage for java.awt AlphaComposite DstOver

Introduction

In this page you can find the example usage for java.awt AlphaComposite DstOver.

Prototype

AlphaComposite DstOver

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Document

AlphaComposite object that implements the opaque DST_OVER rule with an alpha of 1.0f.

Usage

From source file:CompositeEffects.java

/** Draw the example */
public void paint(Graphics g1) {
    Graphics2D g = (Graphics2D) g1;

    // fill the background
    g.setPaint(new Color(175, 175, 175));
    g.fillRect(0, 0, getWidth(), getHeight());

    // Set text attributes
    g.setColor(Color.black);/*from   w ww. j  av a2s.c o m*/
    g.setFont(new Font("SansSerif", Font.BOLD, 12));

    // Draw the unmodified image
    g.translate(10, 10);
    g.drawImage(cover, 0, 0, this);
    g.drawString("SRC_OVER", 0, COVERHEIGHT + 15);

    // Draw the cover again, using AlphaComposite to make the opaque
    // colors of the image 50% translucent
    g.translate(COVERWIDTH + 10, 0);
    g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.5f));
    g.drawImage(cover, 0, 0, this);

    // Restore the pre-defined default Composite for the screen, so
    // opaque colors stay opaque.
    g.setComposite(AlphaComposite.SrcOver);
    // Label the effect
    g.drawString("SRC_OVER, 50%", 0, COVERHEIGHT + 15);

    // Now get an offscreen image to work with. In order to achieve
    // certain compositing effects, the drawing surface must support
    // transparency. Onscreen drawing surfaces cannot, so we have to do the
    // compositing in an offscreen image that is specially created to have
    // an "alpha channel", then copy the final result to the screen.
    BufferedImage offscreen = new BufferedImage(COVERWIDTH, COVERHEIGHT, BufferedImage.TYPE_INT_ARGB);

    // First, fill the image with a color gradient background that varies
    // left-to-right from opaque to transparent yellow
    Graphics2D osg = offscreen.createGraphics();
    osg.setPaint(new GradientPaint(0, 0, Color.yellow, COVERWIDTH, 0, new Color(255, 255, 0, 0)));
    osg.fillRect(0, 0, COVERWIDTH, COVERHEIGHT);

    // Now copy the cover image on top of this, but use the DstOver rule
    // which draws it "underneath" the existing pixels, and allows the
    // image to show depending on the transparency of those pixels.
    osg.setComposite(AlphaComposite.DstOver);
    osg.drawImage(cover, 0, 0, this);

    // And display this composited image on the screen. Note that the
    // image is opaque and that none of the screen background shows through
    g.translate(COVERWIDTH + 10, 0);
    g.drawImage(offscreen, 0, 0, this);
    g.drawString("DST_OVER", 0, COVERHEIGHT + 15);

    // Now start over and do a new effect with the off-screen image.
    // First, fill the offscreen image with a new color gradient. We
    // don't care about the colors themselves; we just want the
    // translucency of the background to vary. We use opaque black to
    // transparent black. Note that since we've already used this offscreen
    // image, we set the composite to Src, we can fill the image and
    // ignore anything that is already there.
    osg.setComposite(AlphaComposite.Src);
    osg.setPaint(new GradientPaint(0, 0, Color.black, COVERWIDTH, COVERHEIGHT, new Color(0, 0, 0, 0)));
    osg.fillRect(0, 0, COVERWIDTH, COVERHEIGHT);

    // Now set the compositing type to SrcIn, so colors come from the
    // source, but translucency comes from the destination
    osg.setComposite(AlphaComposite.SrcIn);

    // Draw our loaded image into the off-screen image, compositing it.
    osg.drawImage(cover, 0, 0, this);

    // And then copy our off-screen image to the screen. Note that the
    // image is translucent and some of the image shows through.
    g.translate(COVERWIDTH + 10, 0);
    g.drawImage(offscreen, 0, 0, this);
    g.drawString("SRC_IN", 0, COVERHEIGHT + 15);

    // If we do the same thing but use SrcOut, then the resulting image
    // will have the inverted translucency values of the destination
    osg.setComposite(AlphaComposite.Src);
    osg.setPaint(new GradientPaint(0, 0, Color.black, COVERWIDTH, COVERHEIGHT, new Color(0, 0, 0, 0)));
    osg.fillRect(0, 0, COVERWIDTH, COVERHEIGHT);
    osg.setComposite(AlphaComposite.SrcOut);
    osg.drawImage(cover, 0, 0, this);
    g.translate(COVERWIDTH + 10, 0);
    g.drawImage(offscreen, 0, 0, this);
    g.drawString("SRC_OUT", 0, COVERHEIGHT + 15);

    // Here's a cool effect; it has nothing to do with compositing, but
    // uses an arbitrary shape to clip the image. It uses Area to combine
    // shapes into more complicated ones.
    g.translate(COVERWIDTH + 10, 0);
    Shape savedClip = g.getClip(); // Save current clipping region
    // Create a shape to use as the new clipping region.
    // Begin with an ellipse
    Area clip = new Area(new Ellipse2D.Float(0, 0, COVERWIDTH, COVERHEIGHT));
    // Intersect with a rectangle, truncating the ellipse.
    clip.intersect(new Area(new Rectangle(5, 5, COVERWIDTH - 10, COVERHEIGHT - 10)));
    // Then subtract an ellipse from the bottom of the truncated ellipse.
    clip.subtract(new Area(new Ellipse2D.Float(COVERWIDTH / 2 - 40, COVERHEIGHT - 20, 80, 40)));
    // Use the resulting shape as the new clipping region
    g.clip(clip);
    // Then draw the image through this clipping region
    g.drawImage(cover, 0, 0, this);
    // Restore the old clipping region so we can label the effect
    g.setClip(savedClip);
    g.drawString("Clipping", 0, COVERHEIGHT + 15);
}

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