What is the best approach to enhance blacked out areas to make the text inside them readable. ??

I am trying to enhance old hand drawn maps which were digitized by scanning and this process has caused some blacked out areas in the image making the text inside them very hard to read.

Here's a sample image :

I tried Adapthist and couple of other histogram based approach but nothing gives me desired result. I could probably lighten the darker shades of grey and make it look a bit better using adapthist but it doesn't really help with the text.

Can i enhance this and get an end result which has only black and white where the lines,text(basically all the information) turns into black(0) and the shades of grey and whiter regions turn into white (255 or 1), Is this even possible ?? If not how close can i even get to it or what is the best solution to get as close as possible to the desired result. Any help is appreciated, Thank you very much !!

I tried hard coding the pixel intensities to the desired level and got to a result like this :

It doesn't look that great but i would be happy enough if i could get rid of all those shades that look like noise and get a crisper text and lines. Thank You!

[dp sb]

Any Help on this please ?

[Steven Lord]

It sounds like you're asking more of an algorithm or technique question, not one directly related to MATLAB. On those types of image analysis and image processing algorithms, MATLAB Answers isn't the best place to ask. There's a tag in Stack Overflow dedicated to image processing questions; perhaps ask there with that tag for an algorithm. Then once you have your algorithm, if you have difficulty implementing that algorithm in MATLAB return here for help with that implementation.

http://stackoverflow.com/questions/tagged/image-processing

Alternately, I remember seeing ImageAnalyst post a link to this bibliography frequently in the newsgroup; perhaps some of the papers or techniques it cites can be of use for your application.

http://iris.usc.edu/Vision-Notes/bibliography/contents.html