php生成验证码详细教程

<?php
//header("content-type:image/png");
$num ='1234';
$imagewidth=60;
$imageheight=18;

$numimage = imagecreate($imagewidth,$imageheight);
imagecolorallocate($numimage,240,240,240);
for($i=0;$i<strlen($num);$i++){
$x = mt_rand(1,8)+$imagewidth*$i/4;
$y = mt_rand(1,$imageheight/4);
$color=imagecolorallocate($numimage,mt_rand(0,150),mt_rand(0,150),mt_rand(0,150));
imagestring($numimage,5,$x,$y,$num[$i],$color);
}

for($i=0;$i<200;$i++){
$randcolor=imagecolorallocate($numimage,rand(200,255),rand(200,255),rand(200,255));
imagesetpixel($numimage,rand()%70,rand()%20,$randcolor);
}
imagepng($numimage);
imagedestroy($numimage);
?>

<?php

   //生成验证码图片

    session_start();

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

  srand((double)microtime()*1000000); 

  $roundnum=rand(1000,9999);

  //把随机数存入session以便以后用

   $_session["sessionround"]=$roundnum;

        $im = imagecreate(58,28);

        $red = imagecolorallocate($im, 255,0,0);

        $blue = imagecolorallocate($im, 0,255,0);

 //局域填充，相当于背景

        imagefill($im,68,30,$red);

   //将四位整数验证码绘入图片

        imagestring($im, 5, 10, 8, $roundnum, $blue);

        for($i=0;$i<50;$i++)   //加入干扰象素

        {

                imagesetpixel($im, rand()%70 , rand()%30 , $black);

        }

        imagepng($im);

        imagedestroy($im);

?>

<td>验证码</td><td width="20%">

     <input name="validt" type="text" size="10" maxlength="4"/></td><td colspan="3" width="80%">

     <img src="/www.111cn.net/validitpicture.php" name="validitpic" align="absmiddle"  /></td>

class image
{
 public $info=array();

 function __construct()
 {
  !extension_loaded('gd') && exit("www.111cn.net提示：服务器环境不支持gd库");
  return true;
 }

 function image()
 {
  $this->__construct();
 }
 
 function thumb($image,$thumb_width=300,$thumb_height=225)
 {
  $info=$this->info($image);
  $scale=min(1,min($thumb_width/$info['width'],$thumb_height/$info['height'])); //按比例缩放
  $thumb_width=intval($info['width']*$scale);
  $thumb_height=intval($info['height']*$scale);
  $createfunc='imagecreatefrom'.($info['type']=='jpg'?'jpeg':$info['type']);
  $im=$createfunc($image);
  $thumb_im=$info['type']!='gif' && function_exists('imagecreatetruecolor')?imagecreatetruecolor($thumb_width,$thumb_height):imagecreate($thumb_width,$thumb_height);
  imagecopyresampled($thumb_im,$im,0,0,0,0,$thumb_width,$thumb_height,$info['width'],$info['height']);
  if($info['type']=='gif' || $info['type']=='png')
  {
   $bgcolor=imagecolorallocate($thumb_im,0,255,0);
   imagecolortransparent($thumb_im,$bgcolor);
  }
  $imagefunc='image'.($info['type']=='jpg'?'jpeg':$info['type']);
  $thumbname='thumb_'.$info['name'].'.'.$info['type'];
  $imagefunc($thumb_im,$info['path'].$thumbname);
  imagedestroy($im);
  imagedestroy($thumb_im);
  return $info['path'].$thumbname;  
 }

 function watermark($image,$pos=9,$watermarkimg='images/watermark.gif',$pct=65,$text='',$w_font=5,$w_color='#ff0000')
 {
  $imageinfo=$this->info($image);
  $source_w=$imageinfo['width'];
  $source_h=$imageinfo['height'];
  $imagecreatefunc='imagecreatefrom'.($imageinfo['type']=='jpg'?'jpeg':$imageinfo['type']);
  $im=$imagecreatefunc($image);
  if(!empty($watermarkimg) && file_exists($watermarkimg)) //添加图片水印
  {
   $iswaterimage=true;
   $watermarkinfo=$this->info($watermarkimg);
   $width=$watermarkinfo['width'];
   $height=$watermarkinfo['height'];
   $watermarkcreatefunc='imagecreatefrom'.($watermarkinfo['type']=='jpg'?'jpeg':$watermarkinfo['type']);
   $watermark_im=$watermarkcreatefunc($watermarkimg);
  }
  else //添加文字水印
  {
   $iswaterimage=false;
   if(!empty($w_color) && strlen($w_color)==7)
   {
    $r=hexdec(substr($w_color,1,2));
    $g=hexdec(substr($w_color,3,2));
    $b=hexdec(substr($w_color,5,2));
   }
   $temp = imagettfbbox(ceil($w_font*2.5), 0, 'fonts/alger.ttf', $text);
   $width = $temp[2] - $temp[6];
   $height = $temp[3] - $temp[7];
   unset($temp);
  }
  switch($pos)
  {
   case 0:
    $wx = mt_rand(0,($source_w - $width));
    $wy = mt_rand(0,($source_h - $height));
    break;
   case 1:
    $wx = 5;
    $wy = 5;
    break;
   case 2:
    $wx = ($source_w - $width) / 2;
    $wy = 5;
    break;
   case 3:
    $wx = $source_w - $width-5;
    $wy = 5;
    break;
   case 4:
    $wx = 5;
    $wy = ($source_h - $height) / 2;
    break;
   case 5:
    $wx = ($source_w - $width) / 2;
    $wy = ($source_h - $height) / 2;
    break;
   case 6:
    $wx = $source_w - $width-5;
    $wy = ($source_h - $height) / 2;
    break;
   case 7:
    $wx = 5;
    $wy = $source_h - $height-5;
    break;
   case 8:
    $wx = ($source_w - $width) / 2;
    $wy = $source_h - $height-5;
    break;
   default:
    $wx = $source_w - $width-5;
    $wy = $source_h - $height-5;
    break;
  }
  if($iswaterimage)
  {
   if($imageinfo['type'] == 'png') {
    imagecopy($im, $watermark_im, $wx, $wy, 0, 0, $width, $height);
   } else {
    imagecopymerge($im, $watermark_im, $wx, $wy, 0, 0, $width, $height, $pct);
   }
  }
  else
  {
   imagestring($im,$w_font,$wx,$wy,$text,imagecolorallocate($im,$r,$g,$b));
  }
  $imagefunc='image'.($imageinfo['type']=='jpg'?'jpeg':$imageinfo['type']);
  $imagefunc($im,$image);
  imagedestroy($im);
  return true;
 }

 function info($image)
 {
  $info=array();
  $info['size']=filesize($image);
  $imageinfo=getimagesize($image);
  $info['width']=$imageinfo[0];
  $info['height']=$imageinfo[1];
  $info['width_height']=$imageinfo[3];
  $info['mime']=$imageinfo['mime'];
  unset($imageinfo);
  $imageinfo=pathinfo($image);
  $info['path']=$imageinfo['dirname'].'/';
  $info['type']=strtolower($imageinfo['extension']); //图片类型，不含'.'
  $info['name']=$imageinfo['filename'];
  unset($imageinfo,$name);
  $this->info=$info;
  return $info;
 }
}