In this example we are going to see how to draw an image with Alpha enabled. The notion of Alpha is quite famous on the graphics world. This will help you to make sharper graphics and make your images look very clear and avoid pixelation.
In short, in order to enable antialiasing in your drawing, you should:
- Create a class tha extends
Componentand overridepaintmethod. - Use
AlphaComposite.getInstance(AlphaComposite.SRC_OVER, alpha)to set the Alpha effect.
Let’s see the code snippet that follows:
package com.javacodegeeks.snippets.desktop;
import java.awt.AlphaComposite;
import java.awt.Component;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Graphics2D;
public class AlphaDrawing {
public static void main(String[] args) {
// Create a frame
Frame frame = new 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;
/**
* 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;
int width = getSize().width-1;
int height = getSize().height-1;
// Draw foreground...
// Draw an oval that fills half window
g2d.fillOval(width/4, height/4, width/2, height/2);
// Draw background...
// Set alpha. 0.0f is 100% transparent and 1.0f is 100% opaque.
float alpha = .3f;
g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, alpha));
// Draw an oval that fills the window
g2d.fillOval(x, y, width, height);
}
}
}
This was an example on how to draw using Alpha effect.
