se vuoi questa è una classe che uso per il ridimensionamento con php delle immagini

Codice PHP:
class Thumbnail
    {

    // Set destination filename
    function setImgSource( $source )
        {
        $this->source = $source;
        }

    // Set maximum size of thumbnail
    function setMaxSize ( $max_width = 100, $max_height = 100 )
        {
        $this->max_width = $max_width;
        $this->max_height = $max_height;
        }


    // Get info about original image
    function getImageData( $data )
        {
        $size = GetImageSize( $this->source );
        
        switch ( $data )
            {
            case 'width':
                return $size[0];
                break;
            case 'height':
                return $size[1];
                break;
            case 'type':
                switch ( $size[2] )
                    {
                    case 1:
                        return 'gif';
                        break;
                    case 2:
                        return 'jpg';
                        break;
                    case 3:
                        return 'png';
                        break;
                    }
                break;
            }        
        }

    // Get info about thumbnail
    function getThumbData( $data )
        {
        $w_ratio = $this->max_width  / $this->GetImageData('width');
        $h_ratio = $this->max_height / $this->GetImageData('height');

        if ( $h_ratio < $w_ratio )
            {
            $height = $this->max_height;
            $width = round( $this->GetImageData('width') * $h_ratio, 0);
            }
        else
            {
            $width = $this->max_width;
            $height = round( $this->GetImageData('height') * $w_ratio, 0);
            }
                
        switch ( $data )
            {
            case 'width':
                return $width;
                break;
            case 'height':
                return $height;
                break;
            }
        }

        
    // Creating a thumbnail
    function Create( $dest )
        {
        $img_des = ImageCreateTrueColor ( $this->GetThumbData('width'), $this->GetThumbData('height') );

        switch ( $this->GetImageData('type') )
            {
            case 'gif':
                $img_src = ImageCreateFromGIF ( $this->source );
                break;

            case 'jpg':
                $img_src = ImageCreateFromJPEG ( $this->source );
                break;

            case 'png':
                $img_src = ImageCreateFromPNG ( $this->source );
                break;
            }

        @ImageCopyResized( $img_des, $img_src, 0, 0, 0, 0, $this->GetThumbData('width'), $this->GetThumbData('height'), $this->GetImageData('width'), $this->GetImageData('height') );

        switch ( $this->GetImageData('type') )
            {
            case 'gif':
                if ( empty( $dest ) )
                    {
                    header( "Content-type: image/gif" );
                    return ImageGIF( $img_des );
                    }
                else
                    {
                    return ImageGIF( $img_des, $dest );
                    }
                    break;

            case 'jpg':
                if ( empty( $dest ) )
                    {
                    header ( "Content-type: image/jpeg" );
                    return ImageJPEG($img_des,'',100);
                    }
                else
                    {
                    return ImageJPEG( $img_des, $dest, 100 );
                    }
                break;

            case 'png':
                if ( empty( $dest ) )
                    {
                    header ( "Content-type: image/png" );
                    return ImagePNG( $img_des );
                    }
                else
                    {
                    return ImagePNG( $img_des, $dest );
                    }
                break;
            }
        }
    } 
e la utilizzi in questo modo (dopo aver incluso il file in cui hai messo la classe nel file in cui la utilizzi)

Codice PHP:
$ImgResize = new Thumbnail; // Start using a class        $ImgResize->setMaxSize(80,80); // Specify maximum size (width, height)                $ImgResize->setImgSource($immagine); // Specify original image filename                $ImgResize->Create(""); //vuoto per output diretto, indirizzo sul server nel caso si volesse salvare l'immagine