vb.net - Grid letters with rectangle OCR -

i have been trying grid each letter rectangle on image (on image there colors white , black). i've started this:

    dim bmp bitmap = label1.image     dim xmax integer     dim ymax integer     xmax = label1.width - 1     ymax = label1.height - 1     dim top, bottom, left, right integer     dim first boolean = true     dim last boolean = false     dim first2 boolean = true     dim last2 boolean = false      dim pen pen = pens.red      x = 0 xmax          y = 0 ymax             bmp.getpixel(x, y)                 if .r = 0 , .g = 0 , .b = 0 , first = true                     left = x                      first = false                     last = true                 elseif .r = 0 , .g = 0 , .b = 0 , last = true                     right = x                  end if             end         next y     next x      y = 0 ymax         x = 0 xmax             bmp.getpixel(x, y)                 if .r = 0 , .g = 0 , .b = 0 , first2 = true                     top = y                      first2 = false                     last2 = true                 elseif .r = 0 , .g = 0 , .b = 0 , last2 = true                     bottom = y                  end if             end         next x     next y     first = true     first2 = true     last = false     last2 = false     dim rect new rectangle(left, top, right - left, bottom - top)     dim g graphics = graphics.fromimage(bmp)     g.drawrectangle(pen, rect)     label1.image = bmp 

it'll check of pixels on image , it'll black ones, draw rectangle around 1 letter couldn't more 1 @ time. still can't use seperate letters.

i'll thankful of responses.