Removing Waffle Grid Pattern

[aksarben]

I use PaintShop Pro X6 version 16.0.0.113x64. If there's a better forum to post this question on, please let me know.

I have a photo extracted from a PDF file that is marred by an unsightly "waffle grid" pattern. You can see the photo online at:

http://www.hymntime.com/tch/img/r/i/s/t ... -1938).jpg.

Can PaintShop Pro X6 6.0.0.113x64 remove this grid pattern? If not, can it be be removed with a more recent version, different product, etc.?

[Jean-Luc]

We have discussed that problem here:
https://forum.corel.com/viewtopic.php?f=56&t=66456

[aksarben]

Thanks, Jean-Luc. I looked at the forum topic you suggested, but it doesn't seem to apply to my use case. That topic involved cleaning up a photo from (apparently) an old newspaper. Mine is different in that the grid artifact is much larger and spaced out.

Or am I missing something?

[Jean-Luc]

Thanks, Jean-Luc. I looked at the forum topic you suggested, but it doesn't seem to apply to my use case. That topic involved cleaning up a photo from (apparently) an old newspaper. Mine is different in that the grid artifact is much larger and spaced out.

Or am I missing something?

Yes, you are missing the FFT plugin. The plugin works better on large images, not reduced images.

[Jean-Luc]

Could you post the image at its original size?
Or post the PDF or the link to access it.

[aksarben]

The photo is at http://www.hymntime.com/tch/img/r/i/s/t ... 938%29.jpg

[aksarben]

What is the "FFT plugin," and where can one get it?

[aksarben]

The original PDF is "The His­to­ry of Ot­ter Tail Coun­ty, Min­ne­so­ta," Vol­ume 2. Its URL is:

https://www.google.com/books/edition/Hi ... frontcover

The photo is of Ditlef Ris­tad be­tween pages 96 and 97

[Jean-Luc]

https://www.google.com/books/edition/Hi ... frontcover

I have no access to the image with your link.
I have found another link in Google Books but the image is softened (see attached).
Do you have another source?

[Jean-Luc]

The photo is at http://www.hymntime.com/tch/img/r/i/s/t ... 938%29.jpg

It is a scan from a printed image showing halftone dots and the image is too small. Difficult to improve.

[Jean-Luc]

What is the "FFT plugin," and where can one get it?

Did you read the complete messages?
They are various methods exposed.
One method is the FFT plugin:
https://forum.corel.com/viewtopic.php?p=375195#p375195
But it doesn't work on your image (too small).

[aksarben]

I downloaded FT_July2008.zip & extracted it to Plugins/EN (I assume EN means English?) Is this where it goes, or should it be extracted one level up in the Plugins folder?

After I launch PSP and search for a "Fast Fourier Transform," I come up dry. No mention of FFT. Even the help topics doesn't mention FFT or Fast Fourier Transform. I don't see a link, button or anything in the app to operate the FFT plugin. What am I doing wrong?

[aksarben]

Well, I've made some progress. I finally found the FFT plugin link under Effects-Plugins. So I opened the original image with the waffle grid pattern and chose FFT. The image changed to red/purple design with four quadrants and a "star" effect in the middle. Don't know where to go from here.

I found some references to this kind of result on Photoshop sites, but couldn't find instructions on what if you use PSP.

Anyone know how to proceed on this?

[Jean-Luc]

When an image shows a regular pattern, like halftone dots seen on newspaper images, that regular pattern is concentrated in "star-like" areas when the FFT plugin is applied to the image. To remove the pattern, remove the "star-like" areas. It means, paint on it. But never touch the central cross. I show the before/after in my message (https://forum.corel.com/viewtopic.php?p=375195#p375195). When done, apply the inverse FFT (IFFT). This will reconstruct the image without the pattern.

But your image doesn't show "star-like" areas and cannot be corrected. It explains why I asked you for a better image.

https://www.youtube.com/watch?v=Du6ENFLAoF4

[aksarben]

Ok, here's the file after applying the FFT