Please try this:
This is a morphological image processing. As an example of algorithm:
Iteratively delete (or erode) pixels inside the object (letter) to shrink it without shortening it or breaking it apart. Note that this is an iterative process. In general, you may stop the iteration after several times. Iterate it 3-5 times gives good and fast result.
You may find third party for this kind of image processing. The following thir party has that function.