OCR low-res image from specified set of characters

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Hello all:
Is there a way in which I provide the super set of characters (no characters to be expected outside the set) to the OCR. I mean to say for example if I know that my images has only [U, T, C, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, :, space] as the only characters, can I feed it to matlab OCR and thus expect better predictions.
Can this help somehow on low res image to increase the accuracy?
Kindly see the attached image I am struggling to get good results with.
Thanks much for your attention. Any thoughts will be immensely helpful.
Regards,
Amit

Risposta accettata

Image Analyst
Image Analyst il 8 Feb 2016
For something like that you can probably just crop out each character and find the area. Then, assuming each character has a unique area, have a look up table where a certain area means the character must be a certain character.
  2 Commenti
Amit
Amit il 8 Feb 2016
Ingenious! So yo mean using functions like 'regionprops'?
Thanks @Image Analyst. Such an approach might be helpful for many other related things though I am just hoping for a simpler solution for this one particular case.
Please let me know if you have functions other than 'regionprops' in mind.
Regards,
Amit
Image Analyst
Image Analyst il 10 Feb 2016
Right. Something like
measurements = regionprops(labeledImage, 'Area');
allAreas = [measurements.Area];
% Define character areas
characterAreas = [300,410,130,500,........] % Whatever they are.
for k = 1 : length(allAreas)
differences = abs(measurements(k).Area - characterAreas);
[~, closestCharacterIndex] = min(differences);
% Now you know what character it is....
end

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Più risposte (2)

Anand
Anand il 8 Feb 2016
Modificato: Anand il 8 Feb 2016
This exact functionality is available in the ocr function. Use the 'CharacterSet' Name-Value pair to achieve this. Something like this:
ocrResults = ocr(yourImage,'CharacterSet','UTC1234567890')
In your case, you may have even more information that you can supply to the ocr function. If it's a valid assumption that the left half of the image only contains characters, you could have two calls to ocr with different ROI's.
For example (this is pseudo-code),
leftROI = [1 1 floor(size(im,2)/2) size(im,1)-1];
ocrLeftResults = ocr(im, leftROI, 'CharacterSet','UTC');
rightROI = [floor(size(im,2)/2)+1 1 floor(size(im,2)/2) size(im,1)-1];
ocrRightResults = ocr(im, rightROI, 'CharacterSet', '0123456789');
  5 Commenti
Anand
Anand il 8 Feb 2016
Amit, that should be perfectly fine. There is a list of supported languages which you can see here.
You need to add the Name-Value pair 'Language'.
Amit
Amit il 10 Feb 2016
Hello Anand, thank you. Its very helpful, though the low resolution of my image I guess is resulting in very bad quality of predictions.
Any thoughts.
Thanks again indeed.

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Amit
Amit il 21 Feb 2016
Dear all:
Opening the question again. I have 2864 files such as one attached. I have not been able to find anything, MATLAB or otherwise that works reliably to give me the OCR out. That was my Sunday.
Any of your kind suggestions/directions will be immensely helpful.
Thanks much.
Amit

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