jsp实现生成中国国旗图片效果代码

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ page cOntentType="image/jpeg" import="java.awt.*,
java.awt.image.*,java.util.*,javax.imageio.*,java.awt.Shape.*,java.awt.geom.*,com.sun.image.codec.jpeg.*" %>
<%
 out.clear();
 response.setContentType("image/jpeg");
 response.setHeader("Pragma","No-cache");
 response.setHeader("Cache-Control","no-cache");
 response.setDateHeader("Expires", 0);
 int width =300;
 int height = width/3*2; 
   double maxR = 0.15, minR = 0.05; 
   double maxX = 0.50, maxY = 0.50; 
   double[] minX = {0.75, 0.85, 0.85, 0.75}; 
   double[] minY = {0.35, 0.45, 0.60, 0.70}; 
 BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
 java.awt.Graphics2D g=(java.awt.Graphics2D)image.createGraphics();
 g.clearRect(0, 0,width,height);
 g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
 //画棋面
 g.setColor(java.awt.Color.red);
 g.fillRect(0, 0, width, height);
 //g.fillRect(50, 50, width, height);
 g.setColor(java.awt.Color.yellow);
 //画大五角星
    double ox = height*maxX, oy = height*maxY;
 g.fill(createPentacle(ox,oy,height*maxR,-Math.PI/2)); 
 //画小五角星
    for(int idx =0;idx <4;idx ++){ 
      double sx = minX[idx]*height, sy = minY[idx]*height; 
      double theta = Math.atan2(oy-sy,ox-sx); 
      g.fill(createPentacle(sx,sy,height*minR,theta)); 
    } 
 g.dispose();
 out.clearBuffer(); 
 out = pageContext.pushBody();
 //ImageIO.write(image, "JPEG", response.getOutputStream());
  ServletOutputStream outStream = response.getOutputStream();
    JPEGImageEncoder encoder =JPEGCodec.createJPEGEncoder(outStream);
    encoder.encode(image);
    outStream.close();
%>
<%!
 public static java.awt.Shape createPentacle(double sx, double sy, double radius,double theta) {
 final double arc = Math.PI / 5;
 final double rad = Math.sin(Math.PI / 10) / Math.sin(3 * Math.PI / 10);
 GeneralPath path = new GeneralPath();
 path.moveTo(1, 0);
 for (int idx = 0; idx <5; idx++) {
  path.lineTo(rad * Math.cos((1 + 2 * idx) * arc),rad * Math.sin((1 + 2 * idx) * arc));
  path.lineTo(Math.cos(2 * (idx + 1) * arc),Math.sin(2 * (idx + 1) * arc));
 }
 path.closePath();
 AffineTransform atf = AffineTransform.getScaleInstance(radius, radius);
 atf.translate(sx / radius, sy / radius);
 atf.rotate(theta);
 return atf.createTransformedShape(path);
 }
%>