The metric implemented in the Image::Density Perl
Module estimates the density of data where there
is data, and has a reasonable correlation with
goodness as judged by humans. That is, if you let
a human look at a set of images and judge quality,
the density values for those images as calculated
here tend to correlate well with the human
judgement (densities that are too high or too low
represent "bad'' images). It is intended for use
on bitonal TIFF images, such as those from
scanning paper documents.
