Ridimensionare immagine in una quadrata con sfondo bianco

[bonox]

Ridimensionare immagine in una quadrata con sfondo bianco

Ciao
tramite questa funzione in php e ajax carico un'immagine che vienne ridimensionata, vorrei che questa immagine venisse inserita in un quadrato con sfondo bianco per diventare l'immagine definitiva, per spiegarmi meglio:
se la mia immagine è 800x600 vorrei che venisse inserita in una immagine quadrata bianca di 500x500 mantenendo le stesse proporzioni e avendo, quindi, un borrdo bianco sopra e uno sotto
grazie

class Resize_Image {

    var $image_to_resize;
    var $new_width;
    var $new_height;
    var $ratio;
    var $new_image_name;
    var $save_folder;

    function resize()
    {
        if(!file_exists($this->image_to_resize))
        {
          exit("File ".$this->image_to_resize." does not exist.");
        }

        $info = GetImageSize($this->image_to_resize);

        if(empty($info))
        {
          exit("The file ".$this->image_to_resize." doesn't seem to be an image.");
        }

        $width         = $info[0];
        $height         = $info[1];
        $mime         = $info['mime'];

        /*
        Keep Aspect Ratio?

        */

        if($this->ratio)
        {
            // if preserving the ratio, only new width or new height
            // is used in the computation. if both
            // are set, use width 

            if (isset($this->new_width))
            {
                $factor = (float)$this->new_width / (float)$width;
                $this->new_height = $factor * $height;
            }
            else if (isset($this->new_height))
            {
                $factor = (float)$this->new_height / (float)$height;
                $this->new_width = $factor * $width;
            }
            else
                exit('neither new height or new width has been set');
        }

        // What sort of image?

        $type = substr(strrchr($mime, '/'), 1);

        switch ($type)
        {
        case 'jpeg':
            $image_create_func     = 'ImageCreateFromJPEG';
            $image_save_func     = 'ImageJPEG';
            $new_image_ext         = 'jpg';
            break;

        case 'png':
            $image_create_func     = 'ImageCreateFromPNG';
            $image_save_func     = 'ImagePNG';
            $new_image_ext         = 'png';
            break;

        case 'bmp':
            $image_create_func     = 'ImageCreateFromBMP';
            $image_save_func     = 'ImageBMP';
            $new_image_ext         = 'bmp';
            break;

        case 'gif':
            $image_create_func     = 'ImageCreateFromGIF';
            $image_save_func     = 'ImageGIF';
            $new_image_ext         = 'gif';
            break;

        case 'vnd.wap.wbmp':
            $image_create_func     = 'ImageCreateFromWBMP';
            $image_save_func     = 'ImageWBMP';
            $new_image_ext         = 'bmp';
            break;

        case 'xbm':
            $image_create_func     = 'ImageCreateFromXBM';
            $image_save_func     = 'ImageXBM';
            $new_image_ext         = 'xbm';
            break;

        default:
            $image_create_func     = 'ImageCreateFromJPEG';
            $image_save_func     = 'ImageJPEG';
            $new_image_ext         = 'jpg';
        }

        // New Image
        $image_c = ImageCreateTrueColor($this->new_width, $this->new_height);

        $new_image = $image_create_func($this->image_to_resize);

        imagealphablending( $image_c, false );
        imagesavealpha( $image_c, true );
        
        ImageCopyResampled($image_c, $new_image, 0, 0, 0, 0, $this->new_width, $this->new_height, $width, $height);

        if($this->save_folder)
        {
            if($this->new_image_name)
            {
                $new_name = $this->new_image_name;//.'.'.$new_image_ext;
            }
            else
            {
                $new_name = $this->new_thumb_name( basename($this->image_to_resize) ).'_resized.'.$new_image_ext;
            }

            $save_path = $this->save_folder.$new_name;
        }
        else
        {
        /* Show the image without saving it to a folder */
           header("Content-Type: ".$mime);

           $image_save_func($image_c);

           $save_path = '';
        }

        $process = $image_save_func($image_c, $save_path);

        return array('result' => $process, 'new_file_path' => $save_path);

    }

    function new_thumb_name($filename)
    {
        $string = trim($filename);
        $string = ereg_replace("%20", " ", $string);
        $string = strtolower($string);
        $string = trim(ereg_replace("[^ A-Za-z0-9_]", "", $string)); // tolto spazio
        $string = ereg_replace("[ tnr]+", "_", $string);
        $string = str_replace(" ", '_', $string);
        $string = ereg_replace("[ _]+", "_", $string);
        

        return $string;
    }
}

[gigi991]

Potresti sottrarre ai valori massimi di larghezza e altezza (500x500?) i valori finali dell'immagine ridimensionata (es.500x300)

Quindi prendi il valore al di sotto del valore massimo (in questo caso 300, ma hai già il check sopra per capire quale dei due avrà bordo bianco) e lo dividi per 2.

Il risultato lo usi come coordinata quando piazzi l'immagine ridimensionata nel quadro bianco.

Credo sia qui:

ImageCopyResampled($image_c, $new_image, $this->margin_x, $this->margin_y, 0, 0, $this->new_width, $this->new_height, $width, $height);