php使用GD库生成验证码

目录

绘图步骤

绘制验证码步骤

代码演示

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();
?>