Java tutorial
/* * Copyright (c) 2000 David Flanagan. All rights reserved. This code is from the * book Java Examples in a Nutshell, 2nd Edition. It is provided AS-IS, WITHOUT * ANY WARRANTY either expressed or implied. You may study, use, and modify it * for any non-commercial purpose. You may distribute it non-commercially as * long as you retain this notice. For a commercial use license, or to purchase * the book (recommended), visit http://www.davidflanagan.com/javaexamples2. */ import java.awt.AlphaComposite; import java.awt.Color; import java.awt.Font; import java.awt.GradientPaint; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Image; import java.awt.Rectangle; import java.awt.Shape; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.awt.geom.Area; import java.awt.geom.Ellipse2D; import java.awt.image.BufferedImage; import javax.swing.JFrame; import javax.swing.JPanel; public class CompositeEffects extends JPanel { Image cover; // The image we'll be displaying, and its size static final int COVERWIDTH = 127, COVERHEIGHT = 190; /** This constructor loads the cover image */ public CompositeEffects() { java.net.URL imageurl = this.getClass().getResource("java2s.gif"); cover = new javax.swing.ImageIcon(imageurl).getImage(); } // These are basic GraphicsExample methods public String getName() { return "Composite Effects"; } public int getWidth() { return 6 * COVERWIDTH + 70; } public int getHeight() { return COVERHEIGHT + 35; } /** 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); 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); } public static void main(String[] a) { JFrame f = new JFrame(); f.addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent e) { System.exit(0); } }); f.setContentPane(new CompositeEffects()); f.setSize(700, 250); f.setVisible(true); } }