Identifying filled circles in a scanned image

[Douglas Douglas]

First of all. Thanks Claudio and nikie for your fast answers.

What I want to do is process the forms automatically. Each circle match a
letter (like in a quiz). So if the user select option A in a row, he fills the
first circle. If he select option C in the next row, he fills the third circle
of that row. Get it?

What I want is to write a script that takes the images and say:
Form 1:
  Options Selected: A, B, C, A, B, C, A, D, E, A
Form 2:
  Options Selected: B, B, B, A, A, A, C, D, E, A
...

I've read the PIL tutorial. I've processed images before using PIL (basic stuff
though). I thought about using the difference method of the ImageChops module.
It almost worked. The problem is that when the scanner takes the pages it
doesn't put it in the same exact position in its bed. There's not a lot of
difference, but there's a little.

I also thought about drawing references in the forms (like a line or an X) I
could look for.

I like to hear your comments now that I explained a little more.



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