PHP使用GIFEncoder类生成gif动态滚动字幕

今天在公司，经理让做一个滚动字幕。但是，不许生成gif图片。所以上网找了gifencoder这个类库。确实很好用，但是，应用过程中也出现了一些问题，现在写在这里，以供后来人参考，少走弯路。

文字滚动分为两种情况。第一种为水平滚动：

<?php
require_once("gifencoder.class.php");
$count=0;   //设置默认计数器
while(true){
    $str = $_request['str'] ? $_request['str']:"暂无输入";
    $length=strlen($str)*9;     //计算行长度，这个计算的比较简单，就是每个字数*9个像素
    $im=imagecreatefromgif("hudongbg.gif");     //根据图片创建图像
    $white = imagecolorallocate($im,255,255,255);       //设置一个白色
    $str = iconv("gb2312","utf-8",$str);        //特别注意的是转换编码，因为之后用到的imagettftext只能用utf-8编码
    $now=220-$count*5;      //当前运行的水平位置
    imagettftext($im,13,0,$now,20,$white,"ziti.ttf",$str);      //根据字体在图片上写文字，参数意思（图像源，文字大小，倾斜角度，水平位置，垂直位置，颜色，使用的字体文件，要写的内容
    imagegif($im);     
    imagedestroy($im);
    $imagedata[] = ob_get_contents();       //创建这一帧的图像数据
    ob_clean();
    $count++;
    if ($now+$length<0){    //如果最后一个文字移动到头，那么结束
        break;
    }
}
$diy[]=0;//开始延迟时间
$gif = new gifencoder($imagedata,$diy,0,2,0,0,0,"bin");
ob_start();
header ('content-type:image/gif');
echo $gif->getanimation();
?>

然后是垂直的：

<?php
/*
从url获得"str=第一行;第二行;第三行"的数据
*/
require_once("gifencoder.class.php");
$array_str=array();
$str=$_get['str'];
/*
将$str转化成数组
*/
if ($str!=''){
    $array_str=explode(";",$str);
}else{
    $array_str=array("欢迎您光临本店！");
}
/*
如果数组元素没有值，清除最后一个“;”
*/
foreach( $array_str as $k=>$v){
    if( !$v )
    unset( $array_str[$k] );
}
for ($i=0,$length=count($array_str);$i<$length;$i++){
    for ($k=0;$k<20;$k++){
        $im=imagecreatefromgif("hudongbg.gif");     //根据图片创建图像
        $white = imagecolorallocate($im,255,255,255);       //设置一个白色
        $test = iconv("gb2312","utf-8",$array_str[$i]);     //特别注意的是转换编码，因为之后用到的imagettftext只能用utf-8编码，注意，一定要用字符串接收，不能用数组，否则会乱码
        $heigth=40-$k;        //当前文字高度
        imagettftext($im,13,0,0,$heigth,$white,"ziti.ttf",$test);        //将文字写入图片
        imagegif($im);
        $imagedata[] = ob_get_contents();
        ob_clean();
    }
}
/*
这里是设置每一张图片的延迟时间，到第20帧的时候，延迟2秒。这样才能出现文字走到顶，停顿一会的效果
*/
$delay=array();
for ($i=1,$length=count($array_str)*20;$i<=$length;$i++){
    if ($i%20==0){
        $delay[$i-1]="200";
    }else{
        $delay[$i-1]="1";
    }
}
$transparent=array(0);
$gif = new gifencoder($imagedata,$delay,0,2,0,0,$transparent,"bin");
ob_start();
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 );
    }
}
?>