Adaptive thresholding for scanned images

I would like to improve a number of images accquired with documen开发者_开发问答t scanning, does anybody have any VB sample code for dynamic thresholding to achieve a result something similar to the images shown at the bottom of the page;

http://www.datastor-ltd.co.uk/component/content/article/39-microfilm-scanning/104-the-benefits-of-scanning-in-greyscale

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Have a look at Otsu's method. It's quite simple an easy to implement -- you should be able to transform Wikipedia's pseudo-code into VB in no time.

Otsu's method will give you a threshold (single value) -- you can then use that threshold to binarize the image. The thresholding code is also trivial.