PHP使用GIFEncoder类生成的GIF动态图片验证码

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 < 32; $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; $k < strlen($authstr); $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 < 20; $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 < 3; $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();
 
}

gifencoder类源码：

<?php
class gifencoder {
    var $gif = "gif89a";                /* gif header 6 bytes        */
    var $ver = "gifencoder v2.06";        /* encoder version                */
    var $buf = array ( );
    var $lop =  0;
    var $dis =  2;
    var $col = -1;
    var $img = -1;
    var $err = array (
    'err00' =>"does not supported function for only one image!",
    'err01' =>"source is not a gif image!",
    'err02' =>"unintelligible flag ",
    'err03' =>"could not make animation from animated gif source",
    );
    /*
    :::::::::::::::::::::::::::::::::::::::::::::::::::
    ::
    ::        gifencoder...
    ::
    */
    function gifencoder        (
    $gif_src, $gif_dly, $gif_lop, $gif_dis,
    $gif_red, $gif_grn, $gif_blu, $gif_mod
    ) {
        if ( ! is_array ( $gif_src ) && ! is_array ( $gif_tim ) ) {
            printf        ( "%s: %s", $this->ver, $this->err [ 'err00' ] );
            exit        ( 0 );
        }
        $this->lop = ( $gif_lop > -1 ) ? $gif_lop : 0;
        $this->dis = ( $gif_dis > -1 ) ? ( ( $gif_dis < 3 ) ? $gif_dis : 3 ) : 2;
        $this->col = ( $gif_red > -1 && $gif_grn > -1 && $gif_blu > -1 ) ?
        ( $gif_red | ( $gif_grn << 8 ) | ( $gif_blu << 16 ) ) : -1;
        for ( $i = 0; $i < count ( $gif_src ); $i++ ) {
            if ( strtolower ( $gif_mod ) == "url" ) {
                $this->buf [ ] = fread ( fopen ( $gif_src [ $i ], "rb" ), filesize ( $gif_src [ $i ] ) );
            }
            else if ( strtolower ( $gif_mod ) == "bin" ) {
                $this->buf [ ] = $gif_src [ $i ];
            }
            else {
                printf        ( "%s: %s ( %s )!", $this->ver, $this->err [ 'err02' ], $gif_mod );
                exit        ( 0 );
            }
            if ( substr ( $this->buf [ $i ], 0, 6 ) != "gif87a" && substr ( $this->buf [ $i ], 0, 6 ) != "gif89a" ) {
                printf        ( "%s: %d %s", $this->ver, $i, $this->err [ 'err01' ] );
                exit        ( 0 );
            }
            for ( $j = ( 13 + 3 * ( 2 << ( ord ( $this->buf [ $i ] { 10 } ) & 0x07 ) ) ), $k = true; $k; $j++ ) {
                switch ( $this->buf [ $i ] { $j } ) {
                    case "!":
                        if ( ( substr ( $this->buf [ $i ], ( $j + 3 ), 8 ) ) == "netscape" ) {
                            printf        ( "%s: %s ( %s source )!", $this->ver, $this->err [ 'err03' ], ( $i + 1 ) );
                            exit        ( 0 );
                        }
                        break;
                    case ";":
                        $k = false;
                        break;
                }
            }
        }
        gifencoder::gifaddheader ( );
        for ( $i = 0; $i < count ( $this->buf ); $i++ ) {
            gifencoder::gifaddframes ( $i, $gif_dly [ $i ] );
        }
        gifencoder::gifaddfooter ( );
    }
    /*
    :::::::::::::::::::::::::::::::::::::::::::::::::::
    ::
    ::        gifaddheader...
    ::
    */
    function gifaddheader ( ) {
        $cmap = 0;
        if ( ord ( $this->buf [ 0 ] { 10 } ) & 0x80 ) {
            $cmap = 3 * ( 2 << ( ord ( $this->buf [ 0 ] { 10 } ) & 0x07 ) );
            $this->gif .= substr ( $this->buf [ 0 ], 6, 7                );
            $this->gif .= substr ( $this->buf [ 0 ], 13, $cmap        );
            $this->gif .= "!/377/13netscape2.0/3/1" . gifencoder::gifword ( $this->lop ) . "/0";
        }
    }
    /*
    :::::::::::::::::::::::::::::::::::::::::::::::::::
    ::
    ::        gifaddframes...
    ::
    */
    function gifaddframes ( $i, $d ) {
        $locals_str = 13 + 3 * ( 2 << ( ord ( $this->buf [ $i ] { 10 } ) & 0x07 ) );
        $locals_end = strlen ( $this->buf [ $i ] ) - $locals_str - 1;
        $locals_tmp = substr ( $this->buf [ $i ], $locals_str, $locals_end );
        $global_len = 2 << ( ord ( $this->buf [ 0  ] { 10 } ) & 0x07 );
        $locals_len = 2 << ( ord ( $this->buf [ $i ] { 10 } ) & 0x07 );
        $global_rgb = substr ( $this->buf [ 0  ], 13,
        3 * ( 2 << ( ord ( $this->buf [ 0  ] { 10 } ) & 0x07 ) ) );
        $locals_rgb = substr ( $this->buf [ $i ], 13,
        3 * ( 2 << ( ord ( $this->buf [ $i ] { 10 } ) & 0x07 ) ) );
        $locals_ext = "!/xf9/x04" . chr ( ( $this->dis << 2 ) + 0 ) .
        chr ( ( $d >> 0 ) & 0xff ) . chr ( ( $d >> 8 ) & 0xff ) . "/x0/x0";
        if ( $this->col > -1 && ord ( $this->buf [ $i ] { 10 } ) & 0x80 ) {
            for ( $j = 0; $j < ( 2 << ( ord ( $this->buf [ $i ] { 10 } ) & 0x07 ) ); $j++ ) {
                if        (
                ord ( $locals_rgb { 3 * $j + 0 } ) == ( $this->col >>  0 ) & 0xff &
                ord ( $locals_rgb { 3 * $j + 1 } ) == ( $this->col >>  8 ) & 0xff &
                ord ( $locals_rgb { 3 * $j + 2 } ) == ( $this->col >> 16 ) & 0xff
                ) {
                    $locals_ext = "!/xf9/x04" . chr ( ( $this->dis << 2 ) + 1 ) .
                    chr ( ( $d >> 0 ) & 0xff ) . chr ( ( $d >> 8 ) & 0xff ) . chr ( $j ) . "/x0";
                    break;
                }
            }
        }
        switch ( $locals_tmp { 0 } ) {
            case "!":
                $locals_img = substr ( $locals_tmp, 8, 10 );
                $locals_tmp = substr ( $locals_tmp, 18, strlen ( $locals_tmp ) - 18 );
                break;
            case ",":
                $locals_img = substr ( $locals_tmp, 0, 10 );
                $locals_tmp = substr ( $locals_tmp, 10, strlen ( $locals_tmp ) - 10 );
                break;
        }
        if ( ord ( $this->buf [ $i ] { 10 } ) & 0x80 && $this->img > -1 ) {
            if ( $global_len == $locals_len ) {
                if ( gifencoder::gifblockcompare ( $global_rgb, $locals_rgb, $global_len ) ) {
                    $this->gif .= ( $locals_ext . $locals_img . $locals_tmp );
                }
                else {
                    $byte  = ord ( $locals_img { 9 } );
                    $byte |= 0x80;
                    $byte &= 0xf8;
                    $byte |= ( ord ( $this->buf [ 0 ] { 10 } ) & 0x07 );
                    $locals_img { 9 } = chr ( $byte );
                    $this->gif .= ( $locals_ext . $locals_img . $locals_rgb . $locals_tmp );
                }
            }
            else {
                $byte  = ord ( $locals_img { 9 } );
                $byte |= 0x80;
                $byte &= 0xf8;
                $byte |= ( ord ( $this->buf [ $i ] { 10 } ) & 0x07 );
                $locals_img { 9 } = chr ( $byte );
                $this->gif .= ( $locals_ext . $locals_img . $locals_rgb . $locals_tmp );
            }
        }
        else {
            $this->gif .= ( $locals_ext . $locals_img . $locals_tmp );
        }
        $this->img  = 1;
    }
    /*
    :::::::::::::::::::::::::::::::::::::::::::::::::::
    ::
    ::        gifaddfooter...
    ::
    */
    function gifaddfooter ( ) {
        $this->gif .= ";";
    }
    /*
    :::::::::::::::::::::::::::::::::::::::::::::::::::
    ::
    ::        gifblockcompare...
    ::
    */
    function gifblockcompare ( $globalblock, $localblock, $len ) {
        for ( $i = 0; $i < $len; $i++ ) {
            if        (
            $globalblock { 3 * $i + 0 } != $localblock { 3 * $i + 0 } ||
            $globalblock { 3 * $i + 1 } != $localblock { 3 * $i + 1 } ||
            $globalblock { 3 * $i + 2 } != $localblock { 3 * $i + 2 }
            ) {
                return ( 0 );
            }
        }
        return ( 1 );
    }
    /*
    :::::::::::::::::::::::::::::::::::::::::::::::::::
    ::
    ::        gifword...
    ::
    */
    function gifword ( $int ) {
        return ( chr ( $int & 0xff ) . chr ( ( $int >> 8 ) & 0xff ) );
    }
    /*
    :::::::::::::::::::::::::::::::::::::::::::::::::::
    ::
    ::        getanimation...
    ::
    */
    function getanimation ( ) {
        return ( $this->gif );
    }
}
?>