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Asked by Soumyadip on 24 Mar 2013

Hi,

I have trying to extract the numbers from a calculator screen image. I am using my laptop webcam to detect the image and simultaneously display the result after image processing. Can anybody please help how to proceed??

Answer by Image Analyst on 24 Mar 2013

Accepted answer

Very very easy. You don't even need to do sophisticated OCR. You merely need to sample the image at known locations for known numbers. Trivial for a 7 segment display. Just read the image at 7 locations. Let's say the locations are

1 2 3 4 5 6 7

Now a "1" would have 2 and 5 lit, and all the others unlit.

A "2" would have 1, 3, 4, 5, & 7 lit and the others unlit.

You can make up a 128 element look up table and use that to read off the number, given an input pattern. it's the same concept but a little more complicated if you have something with more resolution than a 7 segment display.

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Soumyadip on 31 Mar 2013

I tried thresholding the b image but the screen is not getting isolated at all. Actually the screen is not having any distinct property and many corners are also getting thresholded. Can you please provide me a little more code?

Image Analyst on 31 Mar 2013

Sorry but I think I've provided you enough to go on. If I do this, then there will be another problem with another weird image, and I can't go on to do the whole project with you. And I don't have time to delve deeply into any one particular project. I think you have the general concepts enough for you to continue on your own and take pride in ownership of your code. If lab thresholding won't work, try thresholding on RGB and look for large black squares. Of course this won't work the minute you start to look at **black** calculators **instead of white** calculators - see what I mean?

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