1 <?php
 2     //加header头，不然浏览器乱码
 3     header("content-type: image/png");
 4     //创建画布资源
 5    $img = imagecreatetruecolor(500, 500);
 6    //创建颜色
 7    $green = imagecolorallocate($img, 0, 255, 0);
 8    //画椭圆
 9    // imagefilledellipse($img, 200, 200, 100, 100, $green);
10    $r = 100;//半径
11    $degree36 = deg2rad(36);//直角三角形18度，改成弧度
12    $l = 2*$r*sin($degree36);
13    $a = $l*cos($degree36);//长边1长度
14    $b = $l*sin($degree36);//短边1长度
15    $c = $l/2;//短边2长度
16    $d = $r*cos($degree36);//长边2长度
17    //五个顶点坐标
18    $px1 = 200;
19    $py1 = 200;
20    $px2 = $px1+$a;
21    $py2 = $py1+$b;
22    $px3 = $px1+$c;
23    $py3 = $py1+$r+$d;
24    $px4 = $px1-$c;
25    $py4 = $py1+$r+$d;
26    $px5 = $px1-$a;
27    $py5 = $py1+$b;
28     //画多边形，points是顶点坐标数组，num_points是顶点个数,妈蛋这个画不出来五角星，只能拼出来。还不如用直线画
29    $points = array($px1,$py1,$px2,$py2,$px3,$py3,$px4,$py4,$px5,$py5);
30    // imagepolygon($img, $points, 5, $green);
31    //画五条线
32    imageline($img, $px1, $py1, $px3, $py3, $green);
33    imageline($img, $px1, $py1, $px4, $py4, $green);
34    imageline($img, $px2, $py2, $px4, $py4, $green);
35    imageline($img, $px2, $py2, $px5, $py5, $green);
36    imageline($img, $px3, $py3, $px5, $py5, $green);
37 
38    //输出画布图像，终于正常了！
39     imagepng($img);
40    
41 ?>