Not sure if I understood fully but seems like you want to read text from the Images. This is
Optical Character Recognition.
http://en.wikipedia.org/wiki/Optical_character_recognition
You may search on Google to get more information on this.
https://www.google.com/#q=OCR+c%23
Edit
Now I understood what you are trying to achieve. You want to detect straight lines on the Images and then line thickness. Not sure
OCR does it but it may give you a direction for your research area. Please post your findings on this.