It depends on what is being scanned. Say you have a perfectly formatted image, directly taken from a scanner, it's a pretty darn quick process. But from my exp

It depends on what is being scanned. Say you have a perfectly formatted image, directly taken from a scanner, it's a pretty darn quick process. But from my experience, what adds to the slowness is pre-processing the image to make it suitable for OCR, especially tesseract. I still haven't found the magic combination of filters because every image is different, especially if your source them from users camera phones.