简述php设计验证码的过程
php使用GD库生成验证码
一、绘图步骤:
1.创建画布，分配颜色,使用以下两个函数(可以在php手册GD库函数中找到)：
imagecreatetruecolor()
imagecolorallocate()
2.绘画过程：
imagefill()
imagettftext()
imagesetpixel()
imageline()
3.输出图像：
header(“Content-Type:image/png”);
imagepng();
imagejpeg();
4.销毁图片（释放内存）
imagedestroy();
二、绘图具体步骤
生成验证码字符串
private function getCode(){ $str="0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"; $t=''; for($i=0;$i<$this->m;$i++){ $t.=$str[rand(0,$this->type['letter'])]; } return $t; }画出验证码
function drawCode(){ $code=$this->getCode();//获取验证码字符串 imagefill($this->im, 0, 0, $this->bg); for ($i=0; $i <200 ; $i++) { imagesetpixel($this->im, rand(0,$this->width), rand(0,$this->height), rand(0,255)); } imageline($this->im, rand(0,$this->width), rand(0,$this->height), rand(0,$this->width), rand(0,$this->height), rand(0,255)); $c=imagecolorallocate($this->im, rand(0,200), rand(0,200), rand(0,200)); for($i=0;$i<$this->m;$i++){ imagettftext($this->im, 18, rand(-40,40), 8+(18*$i), 24, $c, "georgia.ttf",$code[$i] ); } }输出图像
function printImage(){ $this->drawCode(); header("Content-Type:image/jpeg"); imagepng($this->im); $this->destroy(); } function destroy(){ imagedestroy($this->im); }三、代码演示
<?php/*** 验证码画图类*/class Image { private $width; private $height; private $im; private $bg; private $m; private $type=array('num' => 9,'letter' => 61 ); function __construct($width,$height,$m) { $this->width=$width; $this->height=$height; $this->m=$m; $this->im=imagecreatetruecolor($this->width, $this->height); $this->bg=imagecolorallocate($this->im, 220, 220, 220); } private function getCode(){ $str="0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"; $t=''; for($i=0;$i<$this->m;$i++){ $t.=$str[rand(0,$this->type['letter'])]; } return $t; } function drawCode(){ $code=$this->getCode();//获取验证码字符串 imagefill($this->im, 0, 0, $this->bg); //加干扰点 for ($i=0; $i <200 ; $i++) { imagesetpixel($this->im, rand(0,$this->width), rand(0,$this->height), rand(0,255)); } //加干扰线 imageline($this->im, rand(0,$this->width), rand(0,$this->height), rand(0,$this->width), rand(0,$this->height), rand(0,255)); $c=imagecolorallocate($this->im, rand(0,200), rand(0,200), rand(0,200)); for($i=0;$i<$this->m;$i++){ imagettftext($this->im, 18, rand(-40,40), 8+(18*$i), 24, $c, "georgia.ttf",$code[$i] ); } } function printImage(){ $this->drawCode(); header("Content-Type:image/jpeg"); imagepng($this->im); $this->destroy(); } function destroy(){ imagedestroy($this->im); }}function unit_test(){ $obj=new Image(20*4,30,4); $obj->printImage();}unit_test();?>更多PHP相关知识，请访问小兔网！
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