I was just wondering how accurate can tesseract be for handwriting recognition if used with capital letters all in their own little boxes in a form.
I know you can t
In short, you would have to train the Tesseract engine to recognize the handwriting. Take a look at this link:
Tesseract handwriting with dictionary training
This is what the linked post says:
It's possible to train tesseract to recognize handwriting. Here are the instructions: https://tesseract-ocr.github.io/tessdoc/Training-Tesseract
But don't expect very good results. Academics have typically gotten accuracy results topping out about 90%. Here are a couple references for words and numbers. So if your use case can deal with at least 1/10 errors, this might work for you.
Also here is a good academic article written on this subject:
Recognition of Handwritten Textual Annotations using Tesseract Open Source OCR Engine for information Just In Time (iJIT)