用PHP绘制国旗

01<?php

02$Nationflag = ImageCreate(660, 440);

03ImageColorAllocate ($Nationflag,255,0,0);

04DrawPentacle($Nationflag,180,150,120,120);

05DrawPentacle($Nationflag,80,30,210,50);

06DrawPentacle($Nationflag,120,30,250,100);

07DrawPentacle($Nationflag,180,30,250,160);

08DrawPentacle($Nationflag,100,30,210,210);

09Header('Content-type: image/png');

10ImagePng($Nationflag);

11ImageDestroy($Nationflag);

12 

13/*

14    函数:绘制五角星

15    参数

16        $mFlag:图像标识

17        $mAngle:旋转角度

18        $mRadius:外接圆半径

19        $position_X:绘制坐标X

20        $position_Y:绘制坐标Y

21*/

22function DrawPentacle($mFlag,$mAngle,$mRadius,$position_X,$position_Y){

23    $yellow= imagecolorallocate($mFlag, 255, 255, 0);

24    $PI= 3.14;

25    $theta=54+$mAngle;

26    for($i=0;$i<5;$i++) {//五顶点坐标   

27        $r= $mRadius*sin(18*$PI/180)/sin(54*$PI/180);

28        $points[$i]=array('x'=>$r*cos(($theta+$i*72)*$PI/180)+$position_X,'y'=>-$r*sin(($theta+$i*72)*$PI/180)+$position_Y);

29    }      

30    for($i=0;$i<5;$i++){//五条线坐标

31        $j=$i>2?$i-3:$i+2;

32        $lines[$i] =array('x1'=> $points[$i]['x'],'y1' => $points[$i]['y'],'x2' => $points[$j]['x'],'y2' => $points[$j]['y']);

33    }

34    for($i=0;$i<5;$i++){//五交点坐标 

35        $j= $i>3?0:$i+1;

36        $x12= $lines[$i]['x1'] -$lines[$i]['x2'];

37        $x34= $lines[$j]['x1'] -$lines[$j]['x2'];

38        $y12= $lines[$i]['y1'] -$lines[$i]['y2'];

39        $y34= $lines[$j]['y1'] -$lines[$j]['y2'];

40        $c= $x12 * $y34 - $y12* $x34;

41        $a= $lines[$i]['x1'] *$lines[$i]['y2'] -$lines[$i]['y1'] *$lines[$i]['x2'];

42        $b= $lines[$j]['x1'] *$lines[$j]['y2'] -$lines[$j]['y1'] *$lines[$j]['x2'];

43        $x= ($a * $x34 - $b* $x12) /$c;

44        $y= ($a * $y34 - $b* $y12) /$c;

45        $intersection[$i]=array('x'=>$x,'y'=>$y);

46    }

47    for($i=0;$i<3;$i++){//三个三角形

48        $Polygon[$i] =array($points[$i]['x'],$points[$i]['y'],$points[$i+2]['x'],$points[$i+2]['y'],$intersection[$i+2]['x'],$intersection[$i+2]['y']);   

49        imagefilledpolygon($mFlag,$Polygon[$i], 3,$yellow);

50    }

51     

52}

53?>