# A4 page height in inches (approximately)
  use constant PAGE_HEIGHT => 11; 
  # A4 page width in inches (approximately)
  use constant PAGE_WIDTH => 8;
  my $image= new Image::Magick();
  $image->Read( 'filename.tif' );
  $vertical_size = 
    $image->Get( 'y-resolution' ) * PAGE_HEIGHT;
  $horizontal_size = 
    $image->Get( 'x-resolution' ) * PAGE_WIDTH;