<?php
session_start();//開(kāi)啟會(huì)話
header("Content-type:image/png");//定義為圖片
$im = imagecreatetruecolor(100,30);//創(chuàng)建一個(gè)畫布的大小
$color = imagecolorallocate($im, 255, 255, 255);//填充背景顏色
imagefill($im,0,0,$color);//填充$color顏色于$im畫板區(qū)域從左上角0,0開(kāi)始
$content = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";//驗(yàn)證碼內(nèi)容
$fontsize = "6";//字體大小
$ragcha = "";//聲明一個(gè)空變量，接受驗(yàn)證碼內(nèi)容并保存

for ($i=0; $i < 4; $i++) { 
 //截取字符串
 $char = substr($content,rand(0,strlen($content)-1),1);
 //把得到的內(nèi)容輸入到ragcha里
 $ragcha = $ragcha.$char;
 //設(shè)置x軸與y軸的坐標(biāo)
 $x = $i*(100/4) + rand(5,15);
 $y = rand(5,10);
 //設(shè)置驗(yàn)證碼內(nèi)容顏色
 $fontcolor = imagecolorallocate($im,rand(0,120),rand(0,120),rand(0,120));
 //輸出
 imagestring($im, $fontsize, $x, $y, $char, $fontcolor);
}
//保證驗(yàn)證碼內(nèi)容不丟失
$_SESSION["ragcha"] = $ragcha;

//設(shè)置干擾因素
//1.畫線條
for ($g=0; $g < 3; $g++) {
 //設(shè)置線條顏色
 $line = imagecolorallocate($im, rand(50,100), rand(50,100), rand(50,100));
 //輸出線條
 imageline($im,rand(0,99),rand(0,19),rand(0,99),rand(0,19), $line);
}
//2.給背景加點(diǎn)點(diǎn)
for ($r=0; $r < 300; $r++) {
 //設(shè)置點(diǎn)點(diǎn)顏色
 $point = imagecolorallocate($im, rand(20,180), rand(20,180), rand(20,180));
 //輸出點(diǎn)點(diǎn)
 imagesetpixel($im, rand(0,100), rand(0,30), $point);
}
imagepng($im);//輸出整個(gè)圖片