How to remove gray and dark background from a scanned PDF?

[thebestjeter]

I usually download PDFs file of old books or hard to find titles and many of them have gray or extremely dark backgrounds which makes them difficult to read on my Kindle DXG. I would like to be able to remove the background in those PDF, keeping the foreground intact.

Most of those PDF are poetry, so OCR is simply impossible because of they usually have complex layout.

[DSpider]

Install a printer driver that can extract each page as JPG or PNG. You simply hit File - Print, select the driver and change the options for the target directory, DPI, whatever.

First one looks ok to me. You could use Scan Tailor on those extracted images to produce similar results (black and white instead of grayscale). As far as I know, IrfanView can probably save them with a higher contrast. I think it's File - Batch Convert... I don't remember. I haven't used it in a while.

[frabjous]

You could try unpaper.

[thebestjeter]

Originally Posted by DSpider

Install a printer driver that can extract each page as JPG or PNG. You simply hit File - Print, select the driver and change the options for the target directory, DPI, whatever.

First one looks ok to me. You could use Scan Tailor on those extracted images to produce similar results (black and white instead of grayscale). As far as I know, IrfanView can probably save them with a higher contrast. I think it's File - Batch Convert... I don't remember. I haven't used it in a while.

Thanks. It was very helpful.

[thebestjeter]

Originally Posted by frabjous

You could try unpaper.

Thanks. It looks very, very interesting and helpful, but I have no idea how to run this in a Windows machine. Any clue?

[DSpider]

VirtualBox and a copy of Ubuntu (700 MB LiveCD).

[frabjous]

There's a binary of unpaper for DOS available here -- I must admit I don't have a lot of experience with unpaper in general, and none for Windows (I'm a linux user).