vertical edge of the character

our object is to detect the the vertical edge of character presented in image for exemple a image of any word contain for exemple the text 'laiMin', i need to compute the length of horizontal bar of character 'I' and 'i' and 'M' and to obtain here sum.

i know the method but i can't applicate with matlab.

methode is: detection with spatial filter masks are based on the directional prewit filter

a=[1 1 1 1 1 1 1;0 0 0 0 0 0 0;-1 -1 -1 -1 -1 -1 -1]

and

b=[ -1 -1 -1 -1 -1 -1 -1;0 0 0 0 0 0 0;1 1 1 1 1 1 1]

please help me