alphacanvas.java

AlphaBlending图片透明效果程序是利用j2me中MIDP2.0新特性Alpha混合来实现图片透明的两种演示效果代码

/**源代码由程序员联合开发网(www.pudn.com)会员"周润发"收集、整理、重新编辑
 *Email: [e-mail]
 *QQ号：1103798882
 *欢迎大家与我联系互相交流学习 
 **/
package AlphaPackage;

import java.io.IOException;

import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.Graphics;
import javax.microedition.lcdui.Image;

public class AlphaCanvas extends Canvas implements Runnable {
    
    private Image backgroundImage;
    private int[] maskArray;
    private int imageWidth;
    private int imageHeight;
    private int x;
    private int y;
    private int maskHeight = 0;    
    
    public AlphaCanvas(String imageName) {
        //create the background image
        try {
            backgroundImage = Image.createImage(imageName);            
        }catch(IOException ioe) {
            ioe.printStackTrace() ;
        }
        imageWidth = backgroundImage.getWidth();
        imageHeight = backgroundImage.getHeight();
        
        //create a semi-transparent red mask to cover the background image
        maskArray = new int[imageWidth*imageHeight];
        for (int i = 0; i < imageWidth*imageHeight; i++) {
            maskArray[i] = 0x11FFF000;//alpha coefficient set to 0.3
        }
        
        x = (getWidth() - imageWidth)/2;
        y = (getHeight() - imageHeight)/2;
    }
    
    public void paint(Graphics g) {
        g.setColor(255, 255, 255);
        g.fillRect(0, 0, getWidth(), getHeight());//paint Canvas background white
    	g.drawImage(backgroundImage, x, y, Graphics.TOP|Graphics.LEFT);    	     
        
        //render the semi-transparent mask
        if (maskHeight != 0){
            g.drawRGB(maskArray, 0, imageWidth, x, y, imageWidth, maskHeight, true);
        }
    }
    
    public void run() {
        for(int i = 1; i <= imageHeight; i++) {
            maskHeight = i;
            repaint();
            try {
                Thread.sleep(50);
            }catch(InterruptedException ie) {}
        }
    }
    
}