Increase low-contrast pdf readability

[despeckle]

How should I go about making a scanned pdf with light-grey background and darker grey letters more easily readable?
A page fragment for your reference: http://i.imgur.com/J5akirF.png
Already tried -contrast option and Fred's autolevel script, to no avail.

[fmw42]

try my textcleaner script, and/or IM -brightness-contrast to adjust the contrast

[snibgo]

A simple contrast-stretch works fine:

Code: Select all

convert J5akirF.png -set colorspace RGB -contrast-stretch 4x80% j.png