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Allen.Windhorn at emerson.com Allen.Windhorn at emerson.com
Mon Feb 7 22:39:43 CET 2011


This is a question probably more related to machine vision, but I want
to digitize a lot of hand-drawn graphs that we have accumulated over
the years.  I would like to scan them, have a clerical person select a
line on the graph (maybe in several spots), and get back a set of XY
coordinates of the line.  (A bonus would be to select points on the
axes and enter the values to automatically do scaling.)  To confound
the process, there is a grid on the image, and there are several lines
which may cross each other at various angles.

My first thought is someone must have had this problem before and
solved it -- if so, can I adapt your solution?  (There was a product
available commercially, but it didn't work worth a darn.)

If not, can anyone suggest an approach?  My first thought is to
set an image threshold to convert it to ones and zeros, then do some
kind of line-following algorithm that would take guidance from a
human being.  Fortunately, the desired data form smooth curves.
It will be hard to discriminate between the line and the grid though.

Allen Windhorn, P.E. (MN), CEng  (507) 345-2782
Kato Engineering
P.O. Box 8447, N. Mankato, MN  56002
Allen.Windhorn at emerson.com

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