Java将彩色图片转换为灰色图片

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);
			else
				g.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；
	}
}