Php GD e classi

[Rossella_75]

ciao a tutti!!
una domandina per voi facile facile, ho una classe per le librerie gd come la devo usare?

la classe è in un file php chiamato: gd_library_class.php e questo è il suo contenuto

<?
class thumbnail 
{ 
    var $img; 

    function thumbnail($imgfile) 
    { 
        //detect image format 
        $this->img["format"]=ereg_replace(".*.(.*)$","\1",$imgfile); 
        $this->img["format"]=strtoupper($this->img["format"]); 
        if ($this->img["format"]=="JPG" || $this->img["format"]=="JPEG") { 
            //JPEG 
            $this->img["format"]="JPEG"; 
            $this->img["src"] = ImageCreateFromJPEG ($imgfile); 
        } elseif ($this->img["format"]=="PNG") { 
            //PNG 
            $this->img["format"]="PNG"; 
            $this->img["src"] = ImageCreateFromPNG ($imgfile); 
        } elseif ($this->img["format"]=="GIF") { 
            //GIF 
            $this->img["format"]="GIF"; 
            $this->img["src"] = ImageCreateFromGIF ($imgfile); 
        } elseif ($this->img["format"]=="WBMP") { 
            //WBMP 
            $this->img["format"]="WBMP"; 
            $this->img["src"] = ImageCreateFromWBMP ($imgfile); 
        } else { 
            //DEFAULT 
            echo "Not Supported File"; 
            exit(); 
        } 
        @$this->img["lebar"] = imagesx($this->img["src"]); 
        @$this->img["tinggi"] = imagesy($this->img["src"]); 
        //default quality jpeg 
        $this->img["quality"]=75; 
    } 

    function size_height($size=100) 
    { 
        //height 
        $this->img["tinggi_thumb"]=$size; 
        @$this->img["lebar_thumb"] = ($this->img["tinggi_thumb"]/$this->img["tinggi"])*$this->img["lebar"]; 
    } 

    function size_width($size=100) 
    { 
        //width 
        $this->img["lebar_thumb"]=$size; 
        @$this->img["tinggi_thumb"] = ($this->img["lebar_thumb"]/$this->img["lebar"])*$this->img["tinggi"]; 
    } 

    function size_auto($size=100) 
    { 
        //size 
        if ($this->img["lebar"]>=$this->img["tinggi"]) { 
            $this->img["lebar_thumb"]=$size; 
            @$this->img["tinggi_thumb"] = ($this->img["lebar_thumb"]/$this->img["lebar"])*$this->img["tinggi"]; 
        } else { 
            $this->img["tinggi_thumb"]=$size; 
            @$this->img["lebar_thumb"] = ($this->img["tinggi_thumb"]/$this->img["tinggi"])*$this->img["lebar"]; 
        } 
    } 

    function jpeg_quality($quality=75) 
    { 
        //jpeg quality 
        $this->img["quality"]=$quality; 
    } 

    function show() 
    { 
        //show thumb 
        @Header("Content-Type: image/".$this->img["format"]); 

        /* change ImageCreateTrueColor to ImageCreate if your GD not supported ImageCreateTrueColor function*/ 
        $this->img["des"] = ImageCreateTrueColor($this->img["lebar_thumb"],$this->img["tinggi_thumb"]); 
            @imagecopyresized ($this->img["des"], $this->img["src"], 0, 0, 0, 0, $this->img["lebar_thumb"], $this->img["tinggi_thumb"], $this->img["lebar"], $this->img["tinggi"]); 

        if ($this->img["format"]=="JPG" || $this->img["format"]=="JPEG") { 
            //JPEG 
            imageJPEG($this->img["des"],"",$this->img["quality"]); 
        } elseif ($this->img["format"]=="PNG") { 
            //PNG 
            imagePNG($this->img["des"]); 
        } elseif ($this->img["format"]=="GIF") { 
            //GIF 
            imageGIF($this->img["des"]); 
        } elseif ($this->img["format"]=="WBMP") { 
            //WBMP 
            imageWBMP($this->img["des"]); 
        } 
    } 

    function save($save="") 
    { 
        //save thumb 
        if (empty($save)) $save=strtolower("./thumb.".$this->img["format"]); 
        /* change ImageCreateTrueColor to ImageCreate if your GD not supported ImageCreateTrueColor function*/ 
        $this->img["des"] = ImageCreateTrueColor($this->img["lebar_thumb"],$this->img["tinggi_thumb"]); 
            @imagecopyresized ($this->img["des"], $this->img["src"], 0, 0, 0, 0, $this->img["lebar_thumb"], $this->img["tinggi_thumb"], $this->img["lebar"], $this->img["tinggi"]); 

        if ($this->img["format"]=="JPG" || $this->img["format"]=="JPEG") { 
            //JPEG 
            imageJPEG($this->img["des"],"$save",$this->img["quality"]); 
        } elseif ($this->img["format"]=="PNG") { 
            //PNG 
            imagePNG($this->img["des"],"$save"); 
        } elseif ($this->img["format"]=="GIF") { 
            //GIF 
            imageGIF($this->img["des"],"$save"); 
        } elseif ($this->img["format"]=="WBMP") { 
            //WBMP 
            imageWBMP($this->img["des"],"$save"); 
        } 
    } 
} 
?>

grazie a tutti