[Image-SIG] Welcome to the "Image-SIG" mailing list (Digest mode)

Edward Cannon edward at unicornschool.org
Tue Feb 8 00:12:06 CET 2011

There was a discussion about a related problem a few months back, and
the general consensus was: not really possible. I have done things
like this, very time consuming, limited accuracy. If you want to scan
the data and use it in a document, probably OK. Attempting to retrieve
data from the graph, you will loose lots of precision. I would suggest
that you get data from original sources if you can. If you can't, too
Edward Cannon

On Mon, Feb 7, 2011 at 1:39 PM,  <Allen.Windhorn at emerson.com> wrote:
> Greetings:
> 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.
> Regards,
> Allen
> --
> 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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