I downloaded several e-books from the Superstar e-library and planned to convert them to PDF to read on Dasung e-ink tablets. However, I found that the scanned books had low clarity, low contrast and other problems like deskew and text on the other side that can be seen. The readability on e-book readers is low.

Uncleaned on electronic ink screen

After some processing, I finally got a clear version of the PDF, and was able to read it on the e-ink device.

Cleaned on electronic ink screen

Here are the processing steps that went through.

Original image:

Original

Super-resolution operation on the image to improve clarity:

Recognize the rotation of the text in the image and deskew the image accordingly:

deskewed

Recognize the text in the image and binarize the image by text area to get a version that is only black and white:

black and white

The final PDF of this 203-page book is only 8MB in size, and it supports searching for the text in the PDF.

The above operations are done in one place using ImageTrans.