DIY Book Scanner

I would have to run a comparison test in the morning to be sure. I'll let you know what I find then.

What entered numerical DPI is better served for processing if Scan Tailor rejects the images?

My camera creates JPEGS in a format of 2448x3264. This is what I send into scan tailor. If I enter this number, typically, the image is distorted longer or wider. If I enter an even numbered ratio like 600x600 it appears correct.

univurshul wrote:What entered numerical DPI is better served for processing if Scan Tailor rejects the images?

This prompted me to create a signature. The answer is there.

Thanks, Tulon.

Although I do feel like a complete idiot now for prompting a signature like that...Had no idea there was a tutorial vid online that explained this concept.

Noobs.

Best Regards.

I am going to insert a variation of my signature with a link to the tutorial right into the "Fix DPI" dialog. Entering wrong DPIs is quite a common error.

Dear Tulon

several times I get already scanned images (by other) I want clean with Scantailor

and several times these images have dpi settled to 0 (that is not the real dpi)

How can I find he real dpi?

The video tutorial tells you how.

I just found out that Tulon's method described in the video is not always correct. I just photographed a paperback book printed in a small font, and by using Tulon's method, the DPI comes out to 272. But when I measure the length of one line in the image (in pixels) and in the book (in inches) and divide the two, the DPI jumps up to 364! That's quite a difference.

Sure, no one forces book publishers to fit exactly 6 lines in one inch. Still, it's a reasonable estimate that's expected to produce good results with Scan Tailor. BTW, for books with a small font size, it might be beneficial to make Scan Tailor think it's larger than it is by specifying a lower DPI.

For Mac users as myself, finding the correct DPI works as follows.
I use the shareware GraphicConverter from http://www.lemkesoft.de/. It has some rudimentary processing possibilities and I never needed more. I bet you can do the same in GIMP or whatever...
I double click my image, which usually pop-ups Preview. I select an area ranging from side to side of the book. Then I paste it into a new document in GraphicConverter (cmd-j). Now I go to menu Picture/Size/Scale and uncheck "scale picture". Now I measure in real world the size, and enter the result into the width. For example 24.1 cm into the width form. The size dialog will now calcuate the correct DPI automaticaly...
In my case it was 389 DPI. This is very exact, but in my experience, it could vary a bit with moving from beginning to end of a photographed book. But that doesn't really matter...

I have a German version of GraphicConverter, and simply translated the German menu point to English, the real names could be different...
For explanation two picts...

Select the size:
Calculate the DPI