在servlet中，怎么在已有的jpg图像上，画一个圆圈以生成新的图片？？

Question

在servlet中，怎么在已有的jpg图像上，画一个圆圈以生成新的图片？？

Answer 1

做一个filter， 技术上好像把图片读到imagebuffer，然后根据要求调节，你自己查查

Answer 2

package com.gzh.otherutil.filters;import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.ServletException;
import java.io.*;
import java.util.Date;
import java.awt.*;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
import java.awt.image.BufferedImage;/*
 * @author gzh
 *
 * 图像过滤器
 * 将消息 message和图像融合起来然后输出，相当于重新编辑图像信息
 * 可以将图像中加入版权和商标等信息
 * message在web.xml配置文件的  filter  下的 <filter-class> 下的<init-param>里指定
 */public class ImageFilter
    implements Filter
{
    FilterConfig filterConfig;    public void init(final FilterConfig fConf)
    {
        filterConfig=fConf;
    }    public void destroy()
    {
    }    public void doFilter(final ServletRequest request,
                         final ServletResponse response,FilterChain chain)
        throws java.io.IOException,
        javax.servlet.ServletException
    {
        String message="FilterMessage";
        GenericResponseWrapper wrapper=new GenericResponseWrapper((
            HttpServletResponse)response);
        chain.doFilter(request,wrapper);
        OutputStream out=response.getOutputStream();
        message=filterConfig.getInitParameter("message");        if(contentIsUncachedImage(wrapper)&&message!=null)
        {
            ByteArrayOutputStream imageStream=manipulateImage(message,
                wrapper.output());
            response.setContentLength(imageStream.size());
            response.setContentType("image/jpeg");
            out.write(imageStream.toByteArray());
        }
        else
        {
            out.write(wrapper.output());
        }
        out.flush();
        out.close();
    }    public boolean contentIsUncachedImage(GenericResponseWrapper wrapper)
    {
        if(wrapper.getContentType()!=null)
        {
            if(wrapper.getContentType().startsWith("image/"))
            {
                if(wrapper.output().length>0)
                {
                    return true;
                }
            }
        }
        return false;
    }    public ByteArrayOutputStream manipulateImage(String message,
                                                 byte[] imageData)
        throws ServletException
    {
        ByteArrayOutputStream imageStream;
        Frame frame=null;
        Graphics graphics=null;
        try
        {
            frame=new Frame();
            frame.addNotify();
            MediaTracker mt=new MediaTracker(frame); // frame acts as an ImageObserver
            Image image=Toolkit.getDefaultToolkit().createImage(imageData);
            mt.addImage(image,0);
            mt.waitForAll();
            int w=image.getWidth(frame);
            int h=image.getHeight(frame);
            BufferedImage offscreen=new BufferedImage(w,h,
                BufferedImage.TYPE_3BYTE_BGR);
            graphics=offscreen.getGraphics();
            graphics.drawImage(image,0,0,frame);
            graphics.setColor(Color.white);
            graphics.setFont(new Font("Arial",Font.BOLD|Font.ITALIC,20));
            graphics.drawString(message,9,29);
            graphics.setColor(Color.black);
            graphics.drawString(message,10,30);
            imageStream=new ByteArrayOutputStream();
            JPEGImageEncoder encoder=com.sun.image.codec.jpeg.JPEGCodec.
                createJPEGEncoder(imageStream);
            encoder.encode(offscreen);
        }
        catch(InterruptedException e)
        {
            throw new ServletException(e.getMessage());
        }
        catch(IOException e)
        {
            throw new ServletException(e.getMessage());
        }
        finally
        {
            if(graphics!=null)
            {
                graphics.dispose();
            }
            if(frame!=null)
            {
                frame.removeNotify();
            }
        }
        return imageStream;
    }
}