import java.applet.*;import java.awt.*;import java.awt.image.*;@SuppressWarnings("serial")public class ChangeImageColor extends Applet {/** 灰度变换的算法其实很简单，只要提取每个象素点的红、绿、蓝三原色，然后根据公式：灰度值= 红色亮度值*30%+绿色亮 度值*59%+蓝色亮度值*11%，计算出一个灰度值，并将其作为 红，绿，蓝三原色的新值重新写回显存即可。 */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;public void init() {art = getImage(getDocumentBase(), "test2.png");resize(640, 480);//装入图片；}public void paint(Graphics g) {g.setColor(new Color(0xffffff));g.fillRect(0, 0, getWidth(), getHeight());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("running!", 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;//在彩色与黑白之间变化；}}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；PixelGrabber pg = new PixelGrabber(img, x, y, w, h, pixels, 0, w);try {pg.grabPixels();} catch (InterruptedException e) {System.err.println("interrupted waiting for pixels!");return;}for (int i = 0; i < h; i++) {for (int j = 0; j < w; j++) {// 获得像素的颜色int color = pixels[w * i + j];int alpha = (color & 0xFF000000) >> 24;int red = (int) (((color & 0x00FF0000) >> 16) * 0.3);int green = (int) (((color & 0x0000FF00) >> 8) * 0.59);int blue = (int) ((color & 0x000000FF) * 0.11);color = red + green + blue;color = (alpha << 24) | (color << 16) | (color << 8) | color;//System.out.println(Integer.toHexString(color));//由红，绿，蓝值得到灰度值；pixels[w * i + j] = color;}}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();}public void update(Graphics g) {if (xy == null) {xy = getSize();Buf = createImage(xy.width, xy.height);Bufg = Buf.getGraphics();}paint(g);//修改update方法，避免闪烁；}}
