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Using the FFT filter to remove photgraphic paper texture

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  #61  
Old 11-27-2005, 04:35 AM
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bart_hickman bart_hickman is offline
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BTW, your remaining pattern is manifesting itself as stars along the center axis. The attachement shows the red channel with the contrast enhanced and black marks showing where they were. I'd try smaller dots for actually removing the stars to minimize information loss--I used big dots just to illustrate. The pattern may look different on a full resolution image (I'll check it out tomorrow)--this reduced size image has probably created aliasing.

Bart
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  #62  
Old 11-27-2005, 06:31 PM
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garazon garazon is offline
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Great tutorial Rô! Thanks, I have a few scans I'd just about given up on but now I've got the perfect tool to get them done. I've been playing for the last few days with this thing and it's amazing how much info is stored in just the cental part of the red and green channels. Been toying with manipulating parts of the green channel and was able to increase the contrast/clarity in some images also! (but only very slightly so far, if I get it down to something useful, I'll post back)

Also wanted to share a couple of brushes for PSP 8,9 or X users who might want them so they're attached here.

Thanks again for the tut. Glad I found RetouchPro
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Last edited by garazon; 11-27-2005 at 10:12 PM.
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  #63  
Old 11-28-2005, 01:21 PM
Bmud Bmud is offline
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1. Sorry about the confusion surrounding the fft brush. I fixed the file. (finally)

2. Thanks for all the attempts to figure out the circle pattern. We've been using FFT in the way that you suggested in the tutorial for all images where a 150dpi was acceptable because they were full pages. It still worked after a small median filter. In the case of the image I posted on page 4, the image was so small to begin with, well, you get the idea.

3. Now I'm curious how well the FFT would do at de-interlacing. Probably poor. It most certainly did NOT work when I tried to get some blockiness out of bloating an image to 150%. Just a huge grid of stars.
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Last edited by Bmud; 12-22-2005 at 02:01 PM.
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  #64  
Old 11-28-2005, 08:16 PM
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Cameraken Cameraken is offline
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Great Discussion Here, Thanks Rô, BMud and Bart.

It’s not surprising that there is a lot of confusion with this filter.

When you go to
http://www.pages.drexel.edu/~avc25/archive.htm#FFT

There are two filters available for download.

2D Fast Fourier Transform plugin for Adobe

There are two versions
The top one
Download new version of FFT/IFFT Photoshop plugin - 235Kb (April 2005)
This is the HSL version

The bottom one
Download RGB version of FFT/IFFT Photoshop plugin - 156Kb (April 2005) (Red and Green channels are used instead of Hue and Light to store complex phase and amplitude information)
This is the RGB version which Rô’s tutorial is written for.

All the discussion in the forum regarding FFT prior to mid 2005 relates to the HSL version. Discussion after mid 2005 relates to the RGB version

Very often we have tried to make the distinction by calling the new version FFT-RGB


Ken
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  #65  
Old 11-30-2005, 07:05 PM
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bart_hickman bart_hickman is offline
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FFT question for PSP users

I'm using PSP which doesn't have the RGB channel palette mode found in PS, so I have to use a script that breaks the FFT into it's RGB components in a manner that mimicks the PS channel palette. I was wondering how other PSP users are doing it.

Bart
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  #66  
Old 12-01-2005, 04:53 AM
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garazon garazon is offline
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Hi Bart
Using PSP9 here, and the only way I've found to do it is to split the FFt image into RGB channels, then when done editing, recombine the channels, run IFFT on it, copy and paste as new layer over the original. Setting blend mode to Luminance. Btw, I use Luminance (legacy) mode rather than plain Luminance, looks a bit better to me. It's a couple of extra steps more than what PS appears to use , but not a major thing. I can't see any other way to do it. If you know of something else, please pass it on.

Unrelated to PSP: In regards to using FFT, I was reading up on it's applications somewhere (might have been the Aragon Systems site, I'll have to look it up), I noticed all the examples they and other places used of any application to image manipulation were done on square images, and specfically where the dimensions are multiples of 32 (32, 64, 128, 256.......) and having tried it on a couple of images I can see a slight difference when the FFT technique is applied to a square image. Every little bit helps! I didn't recall seeing this discussed previously, so apologies if it has been.
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  #67  
Old 12-02-2005, 04:45 AM
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Quote:
Originally Posted by garazon
........square images, and specfically where the dimensions are multiples of 32 (32, 64, 128, 256.......) ........ I didn't recall seeing this discussed previously, so apologies if it has been.
No need to aplogize! Yes, we did discuss the subject. You might find the "golfball thread" very interesting.
There, thanks to some great input form Chris (of Reindeergraphics), we went into a few more details of FFT.
The FFT plug-in that we're using here (Alex Chirakov) is easy to use and free. However there is a price - it is less than perfect.
A perfect FFT tool, such as supplied by Reindeergraphics, will work on square, multiples of 2 and the conversion process will not introduce any new noise.
With the Chirakov version there is some noise, BUT seeing as we're usually working with less than pristine images the new noise has un-noticable effects.

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  #68  
Old 12-02-2005, 07:00 AM
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garazon garazon is offline
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Thanks Rô

I read the thread with great interest, and it answered a lot of questions I had. Also followed chris' link to optipix and downloaded the free custom filter, looks intriguing also. This will all prove to be invaluable when it comes to cleaning up a lot of scans I have made where a paper texture needs to be remove. Results have been remarkable so far

Thanks again!

Chester
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  #69  
Old 12-14-2005, 09:39 AM
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FFT Action

Using the FFT process has become (even ) easier!!

Our friend, Stefan has put together an action for the FFT process (7.0 and CS2 tested) which can be found together with the "how to do.." at his site here.

Now with Stefan's action and Bmud's star brush we've got ourselves a pretty good toolkit for removing paper texture from scanned photos.

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  #70  
Old 12-15-2005, 02:35 PM
Bmud Bmud is offline
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Greetings once again. I've been noticing every once in a while that images I run the FFT on have completely black red channels. This was a mystery to me until today.

Apparently the plugin doesn't like images over a certain size. I've been trying to pinpoint the behavior as to reverse engineer some sizing rules or to make a proper bug report, but FFT i so slow while I'm at work that I'm having no luck even with a binary method. Just losing lots of time on the clock. It might also be a RAM problem.

Somewhere around the thus far, i've gotten..

bigger than 2662x2991
smaller than 2862x3191

I'm guessing that this means that 1024*3 = 3072 is the magic number. I'll do some more tests at home with my dual core and 2gb of RAM and see if I get similar results. I've got a 512 stick here.
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