Change the pixel color values of some pixels

[user20157]

Can i somehow change color values of some pixels. For example, on this picture:

http://i.stack.imgur.com/Eq6P0.png

i want to darken the accent marks of words by changing their pixel values to other normal ones 'mặt','bằng','sổ','đỏ' since it renders in accuracy in text extraction using Tesseract library.

[snibgo]

A simple way is with "-level", eg:

Code: Select all

convert Eq6P0.png -level 40%,100% x.png