Identify scanned document is handwritten or printed

Question

Using C#, I'm trying to detect whether a document (Invoice to be more specific) is handwritten or printed.

Edited: I don't have to convert handwritting to actual words. Just have to know that handwritting is existing in the scanned document.

Tried OCR method by checking the percentage of meaningless character exceed certain threshold but often gave wrong result due unexpected behavior such as a line drawn across the printed words which cause OCR to capture wrong result.

Any other recommendation on how can I detect a document is handwritten or printed?

^{Example of Printed Document / Example of Handwritten Document}

Not really specific to c# only as what I'm looking for is a tool to help in identifying handwritting existence in a scanned document. C# is what I'm using primarily now thus mentioned it.

Answer 1

One possible differentiation might be on the number of different colours present in multiple areas of the image. Printed invoices, with the exception of the letter head, generally only have 2 colours, (paper colour & printing colour), while hand written invoices will have at least 3 distinct colours over a significant number of areas, (paper, printing and the ink used for handwriting), the ink colour in pens rarely matches that of printing.

I would suggest testing using the ImageMagick, possibly histogram, from the command line to see if this will work for you. If it looks like it will then Magick.Net should give your application ImageMagick functionality.

You could also look at the percentage of each colour that is aligned with the paper boundaries, printed items & text mostly align well with paper boundaries while handwritten text tends to have a range of alignments - for this sort of analysis you are likely to need to use OpenCV - there are possible C# interfaces. Of course if you are making use of OpenCV 3.3 or later you could also try the deep learning classifiers.