<?PHP

    $filename= "test.jpg";
    list($w,$h,$type,$attr) = getimagesize($filename);
    $src_im = imagecreatefromjpeg($filename);

    $src_x = '0';   // begin x
    $src_y = '0';   // begin y
    $src_w = '100'; // width
    $src_h = '100'; // height
    $dst_x = '0';   // destination x
    $dst_y = '0';   // destination y

    $dst_im = imagecreatetruecolor($src_w,$src_h);
    $white = imagecolorallocate($dst_im,255,255);
    imagefill($dst_im,$white);

    imagecopy($dst_im,$src_im,$dst_x,$dst_y,$src_x,$src_y,$src_w,$src_h);

    header("Content-type: image/png");
    imagepng($dst_im);
    imagedestroy($dst_im);

    ?>