相信很多人都想过如何用php生成gif动画来实现动态图片验证码，以下是实现过程。
imagecode函数通过gifencoder类实现的gif动画的php源代码，有兴趣的朋友可以研究一下。
效果如图：
/**
* imagecode 生成gif图片验证
* @param $string 字符串
* @param $width 宽度
* @param $height 高度
* */
function imagecode($string = '', $width = 75, $height = 25)
{
$authstr = $string ? $string : ((time() % 2 == 0) ? mt_rand(1000, 9999) : mt_rand(10000, 99999));
$board_width = $width;
$board_height = $height;
// 生成一个32帧的gif动画
for($i = 0; $i
{
ob_start();
$image = imagecreate($board_width, $board_height);
imagecolorallocate($image, 0,0,0);
// 设定文字颜色数组
$colorlist[] = imagecolorallocate($image, 15,73,210);
$colorlist[] = imagecolorallocate($image, 0,64,0);
$colorlist[] = imagecolorallocate($image, 0,0,64);
$colorlist[] = imagecolorallocate($image, 0,128,128);
$colorlist[] = imagecolorallocate($image, 27,52,47);
$colorlist[] = imagecolorallocate($image, 51,0,102);
$colorlist[] = imagecolorallocate($image, 0,0,145);
$colorlist[] = imagecolorallocate($image, 0,0,113);
$colorlist[] = imagecolorallocate($image, 0,51,51);
$colorlist[] = imagecolorallocate($image, 158,180,35);
$colorlist[] = imagecolorallocate($image, 59,59,59);
$colorlist[] = imagecolorallocate($image, 0,0,0);
$colorlist[] = imagecolorallocate($image, 1,128,180);
$colorlist[] = imagecolorallocate($image, 0,153,51);
$colorlist[] = imagecolorallocate($image, 60,131,1);
$colorlist[] = imagecolorallocate($image, 0,0,0);
$fontcolor = imagecolorallocate($image, 0,0,0);
$gray = imagecolorallocate($image, 245,245,245);
$color = imagecolorallocate($image, 255,255,255);
$color2 = imagecolorallocate($image, 255,0,0);
imagefill($image, 0, 0, $gray);
$space = 15; // 字符间距
if($i > 0) // 屏蔽第一帧
{
for ($k = 0; $k
{
$colorrandom = mt_rand(0,sizeof($colorlist)-1);
$float_top = rand(0,4);
$float_left = rand(0,3);
imagestring($image, 6, $space * $k, $top + $float_top, substr($authstr, $k, 1), $colorlist[$colorrandom]);
}
}
for ($k = 0; $k
{
$colorrandom = mt_rand(0,sizeof($colorlist)-1);
imagesetpixel($image, rand()%70 , rand()%15 , $colorlist[$colorrandom]);
}
// 添加干扰线
for($k = 0; $k
{
$colorrandom = mt_rand(0, sizeof($colorlist)-1);
// $todrawline = rand(0,1);
$todrawline = 1;
if($todrawline)
{
imageline($image, mt_rand(0, $board_width), mt_rand(0,$board_height), mt_rand(0,$board_width), mt_rand(0,$board_height), $colorlist[$colorrandom]);
}
else
{
$w = mt_rand(0,$board_width);
$h = mt_rand(0,$board_width);
imagearc($image, $board_width - floor($w / 2) , floor($h / 2), $w, $h, rand(90,180), rand(180,270), $colorlist[$colorrandom]);
}
}
imagegif($image);
imagedestroy($image);
$imagedata[] = ob_get_contents();
ob_clean();
++$i;
}
$gif = new gifencoder($imagedata);
header ('content-type:image/gif');
echo $gif->getanimation();
}
有关gifencoder类，可在网络中得到下载~