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 );
    }
}
?>