[bart_hickman]

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

[garazon]

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 Paint Shop Pro 8,9 or X users who might want them so they're attached here.

Thanks again for the tut. Glad I found RetouchPro

[Bmud]

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.

[Cameraken]

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

[bart_hickman]

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

Bart

[garazon]

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 Photoshop 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 Paint Shop Pro: 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.

[byRo]

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.

Rô

[garazon]

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

[byRo]

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.

Rô

[Bmud]

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.

[Bmud]

Guess what. Let's say you're like me and you just scanned a 1x2 inch image at 1200dpi and the moire/patterns are ridiculous. After the FFTRGB filter there are too many stars to count, and the significant patterns are difficult to pick up. Good news. There's a handy guide right under your nose to finding the right stars, the "Key Stars" as I call 'em.

Look at your green channel at 50% zoom.

We've been talking a lot about the red channel but not much about the green one. Turns out that dropping a black star where you see a "cup lid straw hole" is right where you need to be. Use you imagination and discretion to figure out if you need to repeat those stars out further by eyeballing the distance to the main star's center or cardinal axis depending on the behavior of your pattern.

Just stay away from putting black on either axis of the main star without being really accurate with your clicking -- it's what creates that crazy black smoke.

By the way, if you're using my star brush make sure that the Flow is set to 100%. I think I have it saved in the preset as 50% which will mess things up. I'd appreciate if someone let me know if it's OK straight out of the cereal box.

[Cameraken]

Hi Bmud.

I could be wrong here but I don’t think you can save the brush opacity or Flow. When I load your FFT brush the opacity stays as it was previously set. I think this happens with all brushes so I don’t think you can save the Opacity/Flow.

Some interesting ideas there could you post an example of a "cup lid straw hole"

By the way, have you seen this thread?
http://www.retouchpro.com/forums/sho...g+stripes+ugly

There are only 2 stars but they are on the axis. I guess that’s what you mean by Black Smoke.


Ken

[Bmud]

This post is just to let you know that I've recieved everyone's comments about my posts being hard to follow. I'm spell checking and revising and attaching screenshots riiiiight nooow.

[bart_hickman]

This might have been mentioned before, but in the interest of completeness, I thought I would mention that making sure the texture aligns perfectly in the horizontal/vertical directions will simplify the spur pattern and thus improve the final result. That means if you have texture pattern that is somehow at an angle with respect to the photo, it will ease the job if you either rotate the photo in the scanner or rotate it in Paintshop/Photoshop prior to doing the Fourier transform.

I've occasionally seen texture that was slightly non-linear. In that case, see if you can warp the photo to make the pattern as linear as possible prior to the FFT. Then remove the spurs. Then undo the warping on the cleaned photo. If the warping is too severe, then the trick of scanning twice at 0 and 180 degrees might be to only option.

Bart

[Taco]

I've searched for a while for something that would remove the moire (or halftone dot) pattern that is found in magazine prints. I think this has a lot of potential. One complaint that I have is that it's not able to handle a 600 dpi scanned image (at least not a full page). Another is the added "noise" that comes with it. I've been considering buying one of the commercial versions, but can anyone tell me if it can handle larger images?

I think a giant leap forward would be if it were automated. Sure, there's a script, but that is only part of it. I'd like to apply filter and process complete. I wouldn't hesitate to pay for a commercial version if this were the case.

Nice site, and thanks for the help.