Home Java Example Java Swing Graphics2D Use Alpha values to draw in Layers

Use Alpha values to draw in Layers
Posted on: October 1, 2008 at 12:00 AM

In this section, you will studied how to use alpha values to the draw the specific shape in layers.

Use Alpha values to draw in Layers

In this section, you will studied how to use alpha values to the draw the specific shape in layers.

An alpha object produces the alpha value which changes with time specified by the parameters of the alpha object. The alpha value is the graphics state parameter that is used to composite objects to the existing page. At full intensity, objects are opaque. At zero intensity, objects are invisible. As the intensity decreases, the specific shape becomes transparent. It can be a part of vertex or texture.
We are providing you an example which uses the alpha values to show transparency. A frame of size (350,300) is created. The g.fillOval() fills the oval shape with the color defined in the constructor new Color(150, 100, 100, 70) of class Color. The values defined in the constructor are alpha values which shows the transparency.

Here is the code of UseAlphaValues.java


import java.awt.*;

import javax.swing.*;



public class UseAlphaValues extends JFrame {

int width, height;



  UseAlphaValues(String st) {

  this(st, 350, 300);

  }

  UseAlphaValues(String st, int w, int h) {

  setTitle(st);

  setSize(width = w, height = h); 

  setBackground(Color.black);

  }

 public void paint(Graphics g) {

  Color color1 = new Color(150, 100, 100, 70); 

  Color color2 = new Color(75, 150, 200, 125);

  Color color3 = new Color(120, 150, 200, 200);

  g.setColor(color1);

  g.fillOval(0, 0, width / 2, height / 2);

  g.setColor(color2);

  g.fillOval(width / 4, height / 4, width / 2, height / 2);

  g.setColor(color3);

  g.fillOval(width / 3, height / 3, width / 4, height / 4);

  }

  public static void main(String[] args) {

  new UseAlphaValues("Use Alpha values to draw in layers.")

  .setVisible(true);

  }

}

Output will be displayed as:

Download Source Code

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