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About Ilias Tsagklis

Ilias Tsagklis
Ilias is a software developer turned online entrepreneur. He is co-founder and Executive Editor at Java Code Geeks.

Drawing on a Buffered Image

In this tutorial we are going to show you how to Draw on a Buffered Image. This is quite useful when you want to further customize the graphics of your application, if you are not pleased with the original Image.

In short in order to Draw on a Buffered Image one should take the following steps:

  • Load an image from a source usingToolkit.getDefaultToolkit().getImage method
  • Use an ImageObserver to monitor the loading of the image. When the image is fully load the user will be notified
  • Create a buffed image from the source image with a format more close to the custom display environment using GraphicsEnvironmentGraphicsDevice and GraphicsConfiguration to perform several image configurations
  • Use graphics.setColor(Color.red) and graphics.fill(new Ellipse2D.Float(0, 0, 100, 50)) to draw a simple shape in the Image.
  • And simply paint the buffered image in a new Frame

Let’s take a look at the code snippet that follows:

package com.javacodegeeks.snippets.desktop;

import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Component;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GraphicsConfiguration;
import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;
import java.awt.Image;
import java.awt.Toolkit;
import java.awt.Transparency;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import java.awt.image.ImageObserver;

public class BufferedImageDrawing {

    static BufferedImage image;
    static boolean imageLoaded = false;

    public static void main(String[] args) {

  // The ImageObserver implementation to observe loading of the image

  ImageObserver myImageObserver = new ImageObserver() {

    public boolean imageUpdate(Image image, int flags, int x, int y, int width, int height) {

if ((flags & ALLBITS) != 0) {

  imageLoaded = true;

  System.out.println("Image loading finished!");

  return false;

}

return true;

    }

  };

  // The image URL - change to where your image file is located!

  String imageURL = "image.png";

  /**

    * This call returns immediately and pixels are loaded in the background

    * We use an ImageObserver to be notified when the loading of the image

    * is complete

    */

  Image sourceImage = Toolkit.getDefaultToolkit().getImage(imageURL);

  sourceImage.getWidth(myImageObserver);

  // We wait until the image is fully loaded

  while (!imageLoaded) {

try {

    Thread.sleep(100);

} catch (InterruptedException e) {

}

  }

  // Create a buffered image from the source image with a format that's compatible with the screen

  GraphicsEnvironment graphicsEnvironment = GraphicsEnvironment.getLocalGraphicsEnvironment();

  GraphicsDevice graphicsDevice = graphicsEnvironment.getDefaultScreenDevice();

  GraphicsConfiguration graphicsConfiguration = graphicsDevice.getDefaultConfiguration();

  // If the source image has no alpha info use Transparency.OPAQUE instead

  image = graphicsConfiguration.createCompatibleImage(sourceImage.getWidth(null), sourceImage.getHeight(null), Transparency.BITMASK);

  // Copy image to buffered image

  Graphics graphics = image.createGraphics();

  // Paint the image onto the buffered image

  graphics.drawImage(sourceImage, 0, 0, null);

  // Draw on the image

  graphics.setColor(Color.red);

  graphics.fill(new Ellipse2D.Float(0, 0, 100, 50));

  // Make all filled pixels transparent - The image must support transparency

  Color transparent = new Color(0, 0, 0, 0);

  graphics.setColor(transparent);

  graphics.setComposite(AlphaComposite.Src);

  graphics.fill(new Rectangle2D.Float(20, 20, 100, 20));

  graphics.dispose();

  // Create frame with specific title

  Frame frame = new Frame("Example Frame");

  // Add a component with a custom paint method

  frame.add(new CustomPaintComponent());

  // Display the frame

  int frameWidth = 300;

  int frameHeight = 300;

  frame.setSize(frameWidth, frameHeight);

  frame.setVisible(true);

    }

    /**
     * To draw on the screen, it is first necessary to subclass a Component and
     * override its paint() method. The paint() method is automatically called
     * by the windowing system whenever component's area needs to be repainted.
     */
    static class CustomPaintComponent extends Component {

  public void paint(Graphics g) {

// Retrieve the graphics context; this object is used to paint

// shapes

Graphics2D g2d = (Graphics2D) g;

/**

 * Draw an Image object The coordinate system of a graphics context

 * is such that the origin is at the northwest corner and x-axis

 * increases toward the right while the y-axis increases toward the

 * bottom.

 */

int x = 0;

int y = 0;

g2d.drawImage(image, x, y, this);

  }

    }

}

 
This was an example explaining how to Draw on a Buffered Image.

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