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本文实例讲述了jsp实现生成中国国旗图片效果代码。分享给大家供大家参考，具体如下：
图片截图如下：
具体代码如下：
<%@ 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);
}
%>
</div>
将代码另存为jsp文件，放在运行目录下执行即可。
代码在tomcat6.0下测试通过
希望本文所述对大家JSP程序设计有所帮助。
</div>