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OCR Seven Segment Display

Posted on 2013-12-03
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Last Modified: 2013-12-26
Hello, I am trying to write a program that can perform OCR on a seven segment display.  I have been able to use the program to perform OCR on normal text, assuming that the text is large enough on the screen.  When I use an image of a LCD seven segment display the program is unable to differentiate any of the numbers.  Would it be possible to do this?
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Question by:SolveEtCoagula07
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Expert Comment

by:Joe Winograd, EE MVE
ID: 39693344
There are various qualities of OCR software out there – some very bad, some very good, none perfect. What OCR software are you using?

OCR is a particular interest of mine and I have numerous OCR packages. If you'd like to post one of your "seven segment display" files, I'll run it through a few OCR packages and let you know what happens. Be sure not to post anything with personal/private/secure data. Regards, Joe

P.S. You should add the OCR/Scanner Software topic and the Document Imaging topic to get more of the right experts involved.
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Author Comment

by:SolveEtCoagula07
ID: 39693415
I have been using Tesseract 3.  My end goal is to have a webcam watch a device and read the information displayed.  If possible, I would also like for the display changing to trigger the OCR event/function.  I have attached an image as well.  Thanks for the quick reply!
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Expert Comment

by:Joe Winograd, EE MVE
ID: 39693424
Image wasn't attached.
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by:SolveEtCoagula07
ID: 39693431
You are correct... o.0  LCD Seven Segment Display
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Expert Comment

by:Joe Winograd, EE MVE
ID: 39694416
I tried numerous OCR packages. They all failed to OCR the digits with their standard configurations. I eventually got it to work perfectly (it created the text 0.000) by using an OCR product that allows specification of particular fonts – that, imo, was the key to success. Here are the steps I used:

(1) Installed a font called "Let's go Digital", available for download (free) from here:
http://www.fontspace.com/category/led

(2) Cropped the picture to contain just the LED digital readout and changed the green background to white. New image looks like this:
7-segment cropped and green-to-white(4) Used Nuance's OmniPage to perform the OCR:
http://www.nuance.com/for-individuals/by-product/omnipage/index.htm

But it did not work when standard fonts were included, even after I added the LED font. It worked only when I removed all of the other fonts and configured it to use just the LED font, as shown in this setup screen:
OmniPage font setupAs mentioned earlier, after performing these steps, the OCR created the correct text – 0.000 – using OmniPage Pro 18.

I don't know if Tesseract 3 (latest is 3.02) has enough configuration flexibility and workflow capability to implement all of these steps. You may need to switch to some other OCR product. Regards, Joe
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by:SolveEtCoagula07
ID: 39704206
My only other idea is...what if we could detect the black without modifying the image and place lines over it.  If we can track where the lines are, we can determine the char?
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Accepted Solution

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Joe Winograd, EE MVE earned 500 total points
ID: 39705205
What do you mean by "place lines over it"? I'm thinking you may mean something like this:

7-seg-with-gridlinesBut I'm not sure. Please clarify.
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Author Comment

by:SolveEtCoagula07
ID: 39740338
Mr. Winograd,
   You assistance has been great!  I have decided that this method to accomplish my task is not reliable enough.  I have come up with an alternative method and am slowly getting it together piece by piece.  Thank you for your help!
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Author Comment

by:SolveEtCoagula07
ID: 39740379
I've requested that this question be closed as follows:

Accepted answer: 0 points for SolveEtCoagula07's comment #a39740338

for the following reason:

A different method was used to accomplish the same task.
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Expert Comment

by:Joe Winograd, EE MVE
ID: 39740375
> You assistance has been great!

Thank you for saying that! I really appreciate hearing it.

> Thank you for your help!

You're welcome. Happy to help. However, the way you're closing this question, I will receive no points for my assistance in helping you. If that's what you intended to do, that's fine with me – it's your call. But I'm bringing it to your attention in the event that you meant to close it in a different way that would give me some credit/points. For example, you may still select your own answer as the Accepted Solution, but accept one or more of my comments as an Assisted Solution, which would provide me with some points for helping you. Again, whatever you prefer to do is fine with me. Regards, Joe
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Expert Comment

by:Joe Winograd, EE MVE
ID: 39740383
Thanks for doing that – much appreciated!
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