JAVA Applet灰阶变换

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改正了JAVA案例开发集锦中案例五的错误

import java.applet.*;import java.awt.*;import java.awt.image.*;public class tt4 extends Applet {/** * */private static final long serialVersionUID = 1L;Image art,Buf;int onced = 0;boolean is_color = true;Graphics Bufg;//使用双缓冲区技术抑制闪烁Dimension xy = null;//存储一个对象的尺寸public void init(){art = getImage(getDocumentBase(),"test.jpg");resize(640, 480);//装入图片}public void paint(Graphics g){if(onced == 0){//如果是第一次装入图片，则直接显示g.drawImage(art,0,0,this);}if((onced == 1) || (onced == 2)){//如果正在进行灰度变换，则提示等待g.setColor(new Color(255,200,0));g.drawString("正在转换~", 1, 30);}if(onced == 3){//如果灰度变换完毕，则显示结果if(is_color)g.drawImage(Buf,0,0,this);elseg.drawImage(art, 0, 0, this);is_color = !is_color;//在彩色与黑色直接变化}}public boolean mouseDown(Event evt, int x, int y){if(onced == 0){onced = 1;}repaint();//用鼠标触发事件return true;}public boolean mouseUp(Event evt, int x, int y){if(onced == 1){onced = 2;int wd = art.getWidth(this);//取得图片宽int ht = art.getHeight(this);//取得图片高GetPixels(art,0,0,wd,ht);//调用灰度变换方法}return true;}public void GetPixels(Image img, int x, int y, int w, int h){int[] pixels = new int[w*h];//定义一块内存空间int gray;PixelGrabber pg = new PixelGrabber(img, x, y, w, h, pixels, 0, w);try{pg.grabPixels();//读取像素值}catch (InterruptedException e){System.err.println("interrupted waiting for pixels!");//return ;}for(int j = 0; j < h; j++){//长宽不要弄错了*******for(int i = 0; i < w; i++){gray = (int)(((pixels[w*j+i]>>16)&0xff)*0.3);gray +=(int)(((pixels[w*j+i]>>8)&0xff)*0.59);gray += (int)(((pixels[w*j+i])&0xff)*0.11);//由红，绿，蓝值得到灰度值pixels[w*j+i] = (255<<24)|(gray<<16)|(gray<<8)|gray;}}Image pic = createImage(new MemoryImageSource(w, h, pixels, 0, w));Bufg.drawImage(pic, 0, 0, this);//显示黑白图片onced = 3;repaint();}@SuppressWarnings("deprecation")public void update(Graphics g){if(xy == null){xy = this.size();Buf = createImage(xy.width, xy.height);Bufg = Buf.getGraphics();}paint(g);//修改update的方法}}

HTML代码

<html><head><title>对彩色图片进行灰度变换</title><body><p align="center"><applet code=tt4.class name=test.jpg width=440 height=440 > </applet></body></html>