PHP学习笔记（4）GD库画五角星

    

 <?php

     //加header头，不然浏览器乱码

     header("content-type: image/png");

     //创建画布资源

    $img = imagecreatetruecolor(500, 500);

    //创建颜色

    $green = imagecolorallocate($img, 0, 255, 0);

    //画椭圆

    // imagefilledellipse($img, 200, 200, 100, 100, $green);

    $r = 100;//半径

    $degree36 = deg2rad(36);//直角三角形18度，改成弧度

    $l = 2*$r*sin($degree36);

    $a = $l*cos($degree36);//长边1长度

    $b = $l*sin($degree36);//短边1长度

    $c = $l/2;//短边2长度

    $d = $r*cos($degree36);//长边2长度

    //五个顶点坐标

    $px1 = 200;

    $py1 = 200;

    $px2 = $px1+$a;

    $py2 = $py1+$b;

    $px3 = $px1+$c;

    $py3 = $py1+$r+$d;

    $px4 = $px1-$c;

    $py4 = $py1+$r+$d;

    $px5 = $px1-$a;

    $py5 = $py1+$b;

     //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

    $points = array($px1,$py1,$px2,$py2,$px3,$py3,$px4,$py4,$px5,$py5);

    // imagepolygon($img, $points, 5, $green);

    //画五条线

    imageline($img, $px1, $py1, $px3, $py3, $green);

    imageline($img, $px1, $py1, $px4, $py4, $green);

    imageline($img, $px2, $py2, $px4, $py4, $green);

    imageline($img, $px2, $py2, $px5, $py5, $green);

    imageline($img, $px3, $py3, $px5, $py5, $green);

    //输出画布图像，终于正常了！

     imagepng($img);

 ?>