Seeking Guidance RE Digitizing of Old Book

[DBinSJ]

I'm trying to digitize an old Russian-language book, to put it up on Google Books and similar platforms, for open access.

Increasing the contrast by 50 (under Colors/Brightness-Contrast) seems to help with readability.

A sample of the unaltered version has been uploaded here. 
A sample of the same page, with contrast increased by 50 has been uploaded here.

I'm seeking advice as to whether (a) the version with the contrast increased is indeed more readable and (b) there would be a better way of changing the image, to maximize readability—or have I likely hit the sweet spot?

Any feedback/suggestions would be most appreciated. I'm a novice with regard to Gimp and similar programs.

[Ofnuts]

Yes, more readable.

Since the color balance isn't perfect, you get a yellow cast when you push contrast, so you should transform the image to black and white (Color>Desaturate).

Otherwise, a better technique

1. Desaturate the image (Color>Desaturate)
   
2. Use the color picker to set the background color from an area on the page (typically, a margin)
   
3. Decompose the image use Filters>Enhance>Wavelet decompose. The Residual layer at the bottom shows the non-uniform lighting of the page
   
4. Bucket-fill that Residual with the color you sampled at step 2)
   
5. You can increase the sharpness of the characters by duplicating the top layer(s) (Scale 1, Scale 2). At that point adding contrast may be unnecessary.
   
6. If you want to add contrast, create a layer with Layer>New from visible and drag it to the top (you can also use Image>Flatten image) and work on that., but you'll need much less contrast.
   

   

[denzjos]

Another option is first desaturate  (Colours / Desaturate / Desaturate)
Then (Filters / Artistic / Photocopy):

   

[Blighty]

1) Desaturate

2) GMIC > Repair > Repair Scanned Document

   

3) Colours > Curves

   

4) Perspective

5) Scale (stretch horizontally)

6) Crop

For one page that can be done. But for whole book it will pay to have the camera properly set-up and get good lighting. Less processing afterwards. And that also means less distortion.

[DBinSJ]

(09-26-2020, 06:46 AM)Thank you so much for taking the time to offer such a conscientious response. I really appreciate it! I am posting a group response below. Wrote: ====================


Yes, more readable.

Since the color balance isn't perfect, you get a yellow cast when you push contrast, so you should transform the image to black and white (Color>Desaturate).

Otherwise, a better technique

1. Desaturate the image (Color>Desaturate)
   
2. Use the color picker to set the background color from an area on the page (typically, a margin)
   
3. Decompose the image use Filters>Enhance>Wavelet decompose. The Residual layer at the bottom shows the non-uniform lighting of the page
   
4. Bucket-fill that Residual with the color you sampled at step 2)
   
5. You can increase the sharpness of the characters by duplicating the top layer(s) (Scale 1, Scale 2). At that point adding contrast may be unnecessary.
   
6. If you want to add contrast, create a layer with Layer>New from visible and drag it to the top (you can also use Image>Flatten image) and work on that., but you'll need much less contrast.
   

---

(09-26-2020, 09:26 AM)Thank you so much for taking the time to offer such a conscientious response. I really appreciate it! I am posting a group response below.='=================== denzjos Wrote: Another option is first desaturate  (Colours / Desaturate / Desaturate)
Then (Filters / Artistic / Photocopy):

---

(09-26-2020, 10:32 AM)Thank you so much for taking the time to offer such a conscientious response. I really appreciate it! I am posting a group response below.='=================== Blighty Wrote: 1) Desaturate

2) GMIC > Repair > Repair Scanned Document



3) Colours > Curves



4) Perspective

5) Scale (stretch horizontally)

6) Crop

For one page that can be done. But for whole book it will pay to have the camera properly set-up and get good lighting. Less processing afterwards. And that also means less distortion.

---

I'd like to thank @Ofnuts, @denzjos and @Blighty for taking the time to respond conscientiously to my posted question. I upgraded to what is apparently the latest version of Gimp (2.10.20). Because of my lack of facility with the program, I wasn't able to accomplish much (my fault entirely).

I think @Blighty made an excellent point when he suggested that I try to set up the camera properly, as there are about 140 pages involved here. It's a Samsung Galaxy Note 5 and I must admit that I'm not very good with adjustments but that's what I'm going to look into next. Maybe there's a forum somewhere for that, where I can get some good advice about setting up that camera for this purpose.

Thank you all again so much for responding to my quest for help with this!

[Krikor]

Remembering that the technique discussed in the thread "Flattening a scanned book", in this forum, can be perfectly complementary to the needs raised in this thread.

In my example I used the approach shown by rich2005 at https://www.gimp-forum.net/Thread-Flatte...5#pid37075 to align the text a little more. So I applied the steps from post #2.