use Image::Magick;
  ...
  # Check and change image height if necessary
  my ($height,$width);
  ($height,$width) = $image->GetAttribute('height','width');
  if ( $height > 300 ) {
    my ($newheight,$newwidth);
    $newheight = 300;
    $newwidth = ($width*$newheight)/$height;
    $image->Scale('height'=>$newheight,'width'=>$newwidth);
  }
  
  # Check and change image width if necessary
  ($height,$width) = $image->GetAttribute('height','width');
  if ( $width > 250 ) {
    my ($newheight,$newwidth);
    $newwidth = 250;
    $newheight = ($height*$newwidth)/$width;
    $image->Scale('width'=>$newwidth,'height'=>$newheight);
  }