Am I correct that the tick-encoding is the only way?

Yes.

is there a reason why it is not implemented using number-recognition?

Not enough time and skills to code something reliable.

(so I should not try implementing it)

Contributions are very welcome!

Alexis Bienvenüe wrote:

Am I correct that the tick-encoding is the only way?

Yes.

is there a reason why it is not implemented using number-recognition?

Not enough time and skills to code something reliable.

But names are recognized? - or am I mistaken here?

I thought opencv had standard implementations for such a thing using something like mnist, but I get your point.

(so I should not try implementing it)

Contributions are very welcome!

I opened a 7000 line Perl file... wouldn't know where to start ;)

Perhaps I'll make it before exams in June. For 300 students, I find named sheets unhandy. For a computer-science multiple choice exam, I find student-id tick-encoding unhandy, but it is of course the most reliable.

But names are recognized?

No. The user has to read the names (the GUI helps her to do this as easily/quickly as possible)

I opened a 7000 line Perl file... wouldn't know where to start ;)

Yes, I'm unfortunately not a programmer.
Can you code something that reads the digits from a box image using OpenCV? You can find some test images here: http://docs.passoire.fr/alexis/amc/local.tgz

I might be able to look into that. Looking into it, I am not sure OpenCVs classification algorithms are the best solution. One might look into neural networks e.g. tensorflow - I've seen mentions of 97-99% accuracy from sample implementations.

I am not sure if I should be worried about false identification. It might not be a problem since the number read should be found in the list of students. For student-ids containing letters, there might be a problem though, but perhaps there is a data-set available for letters too.

From a discussion at the coffee machine, it turns out the encoding might not be such a bad idea after all: the have so bad hand-writing that the secretaries can't read the numbers they are writing.

I will create a test-set so they can practice.

Thanks for your quick response.