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FFT and Golf Balls

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  #51  
Old 05-28-2005, 10:34 AM
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jcr6 jcr6 is offline
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Black is right

Black means zero -- that there is no power to that frequency or that that particular sine wave should not be present. You should erase to black. 50% gray would be a pretty significant amplitude for that frequency. You'd essentially be ADDING a pattern.

Since I'm a mac person, I haven't tried Alex's plugins. I presume that they don't work in 16-bits? That's unfortunate because you loose a lot of (useful/important) precision by only working in 8-.

One of the reasons that you can get into trouble in Fourier space is just that gooey mess you've been talking about. The ONLY safe operation that you can perform by hand on a power spectrum is to change the amplitude (AND NOT THE PHASE) of a frequency. This means lighten or darken. I suspect that a better workflow would be:

1) Do the FFT
2) Go into QuickMask
3) Mark the spikes (stars, whatever you call them) with a paintbrush in the mask -- use a fairly large brush, one that is big enough to completely remove the spike and a little bit of the neighborhood. Also use a brush with soft edges. A hard edge will cause ringing artifacts.
4) exit QuickMask
5) Use Levels to reduce the value to black of the spikes. This will preserve the color information (e.g. the Phase)
6) Do the iFFT

-Chris

P.S. We have a lot of bare forehead between us. -- Should I make my image be B&W?
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File Type: jpg jcr6bw.jpg (1.9 KB, 134 views)
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  #52  
Old 05-28-2005, 07:40 PM
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Cameraken Cameraken is offline
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Krisna
Thanks for the suggestions. It took some finding but I found them
Astra Image
This is available here
http://www.phasespace.com.au/download.htm
This Program can be used Free of charge but with save disabled until you have paid $AU49.95 for it

The next Program looks much more promising.
Image J It is part of The Image Processing Toolkit
Available Here for Free
http://rsb.info.nih.gov/ij/download.html
ImageJ runs on Linux, Mac OS 9, Mac OS X and Windows
The Docs are here
http://rsb.info.nih.gov/ij/docs/
And the bit about FFT is here
http://rsb.info.nih.gov/ij/docs/menus/process.html#fft

It is Not a plugin but a complete program

Just one problem Krishna I can’t get it to work
I loaded my image
Process > FFT > FFT
Painted out the stars with the Paintbrush tool in Black
Process > FFT > InverseFFT

I suppose I could have a Bad copy but the results came back exactly the same as they went in.

Krishna. Does that sound OK.
If it does I’ll try downloading it again

Ken
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  #53  
Old 05-28-2005, 10:09 PM
krishna krishna is offline
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Quote:
Originally Posted by Cameraken
Thanks for the suggestions. It took some finding but I found them
Astra Image
Ken
I find this software extremely easy to edit the FFT. Moreover the algorithms this programme uses for re-focusing blurred pictures works excellent, sometimes.

Quote:
Originally Posted by Cameraken
Just one problem Krishna I can’t get it to work
I loaded my image
Process > FFT > FFT
Painted out the stars with the Paintbrush tool in Black
Process > FFT > InverseFFT

I suppose I could have a Bad copy but the results came back exactly the same as they went in.

Krishna. Does that sound OK.
If it does I’ll try downloading it again

Ken
Ken, I am surprised at this result. First I thought may be the FFT is not working because of you doing it in RGB mode. So far I have been doing it in grayscale mode. Today, thanks to you, I tried on the colour version of the figure and it worked. The method you used is correct but I am unable to say what is going wrong. Could you check the version of Java running on your machine?

--
thanks
Krishna
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  #54  
Old 05-29-2005, 12:20 AM
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Quote:
Originally Posted by jcr6
Black means zero -- that there is no power to that frequency or that that particular sine wave should not be present. You should erase to black. 50% gray would be a pretty significant amplitude for that frequency. You'd essentially be ADDING a pattern.
I made the attached on Friday and discounted it because of the banding around the edges but given the recent discussions concerning cloning, erasing to black, et al, maybe there's some value. Apart from the outside banding the image to me looks as good or better than Chris's.
All I did was use the Lasso around each of the "stars", deleted, then ran Ifft.
Is there a simple reason to explain the perimeter banding?

Dave
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File Type: jpg ChrisvsDeleteStars.jpg (69.2 KB, 46 views)
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  #55  
Old 05-29-2005, 12:38 AM
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Caitlin Caitlin is offline
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Quote:
Originally Posted by Duv
All I did was use the Lasso around each of the "stars", deleted, then ran Ifft.
Dave, when you say 'delete' what do you mean exactly?
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  #56  
Old 05-29-2005, 08:04 AM
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jcr6 jcr6 is offline
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"Banding" is officially called "Ringing"

Duv: The problem with the lasso method is that you have a sharp cutoff of where there is data to where there isn't. If you feathered your selection (by, say 2 pixels) before you deleted, and made the selection correspondingly larger, I'd say you've got a good method.

That problem you're seeing is well known. Very well known. This is why in mine when people provide pass masks (essentially a quickmask), we "suggest" that they blur them first. This smooths out the step function in frequency space, which in turn prevents ringing.

This is also why I suggested painting in the Quickmask with a soft brush -- you get soft edges to the holes in the frequency map.
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  #57  
Old 05-29-2005, 09:36 AM
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Cameraken Cameraken is offline
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Krishna

I uninstalled ij134-jdk15-setup.exe and downloaded ij133-setup.exe now its working fine.
Astral Image needs a greyscale image but image J works in full colour.
Image J will remain on my PC as a quick easy option
Thanks again for the suggestion.
There also appears to be a lot of other useful tools included which I’ll look at later.

Jcr6. You should look at image J. It may be of interest (and it works on a mac as its Java)

Byro
Image J paints out the stars in Black
Astral Image darkens them
Jcr6 recommends Black
It looks like Darker or Black and not cloning is the correct method

Another interesting point
Image J – when I give it my sample image (which is 322 X 442 pixels)
The FFT is 512 x 512 so it’s automatically taken it to a square power of 2

Try This
Image J
Load picture
Process > FFT >FFT
Now before painting And with FFT selected
Process > Enhance Contrast > Saturated Pixels 1%
Good Eh!
Now you see stars that were not visible before
Paint out all the stars except the big one in the middle
Process > FFT > InverseFFT

Ok the picture still isn’t perfect But I believe this is the best this version of FFT will do.
If anybody has got better then I think they have done further manipulation.

Does anyone want to discuss which version of FFT is best?
Byro. Is Alex Chirakov FFT version the best? Or is it the only one you found?

These pictures are a straight before and after with no additional manipulation

Ken
Attached Images
File Type: jpg RetouchProPosting.jpg (21.6 KB, 40 views)
File Type: jpg FFT of RetouchProPosting.jpg (92.8 KB, 45 views)
File Type: jpg Inverse FFT of RetouchProPosting.jpg (17.6 KB, 56 views)
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  #58  
Old 05-29-2005, 10:27 AM
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Ken, I still am seeing residual golfballs but not sure why cause I used a similar method. Thanks to Chris's suggestion, I 2 pixeled my Lasso and got these results. Still a bit of "Ringing" at top left but otherwise I'm a pretty happy camper. This was using FFT RGB. Still haven't figured out Chris's method. Well, going to work on some other texture problems.

Caitlin, sorry, when I selected a "star" I just hit the delete button and moved to the next.

Cheers
Dave
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File Type: jpg D-BlackHoles.jpg (89.2 KB, 38 views)
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  #59  
Old 05-29-2005, 11:37 AM
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Been away a few days and missed vital information about FFT .... Gosh I have a lot to catch up now!!!

Quote:
Originally Posted by Cameraken
Floras has obviously been manipulated so its hard to compare.
... If for 'manipulated' you intend run through FFT/IFFT ... yes .. but no other kind of 'manipulation was done in the middle (grey) picture attached to my previous post.
I've only used the 'old' HSB Alex Chirokov FFT plug-in for Photoshop to get that result .... for what I can see it has become 'old fashioned' already but, while I read all this new informations, here is what my HSB channels look like ...

First I 'healed' out the stars in the Blue Channel (figure1), then in the Green Channel (figure 2) and finally I 'cleaned' the 'composite' RGB (figure 3).

One last thing .... I found that the 'banding around the edges' appears whenever the the cross' arms are involved in the 'cleaning' ...
Attached Images
File Type: jpg CropBlue.jpg (95.0 KB, 24 views)
File Type: jpg CropGreen.jpg (52.5 KB, 25 views)
File Type: jpg CropHSB.jpg (93.8 KB, 28 views)
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  #60  
Old 05-29-2005, 12:21 PM
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The fast Fourier transform (FFT) is a discrete Fourier transform algorithm which reduces the number of computations needed for N points From 2N^2 to 2NlgN…….
Bla Bla Bla.
Our tests performed on on a variety of platforms, show that FFTW's performance is typically superior to that of other publicly available FFT software, and is even competitive with vendor-tuned codes. In contrast to vendor-tuned codes, however, FFTW'………..
Bla Bla Bla.
Hence the name, "FFTW," which stands for the somewhat whimsical title of "Fastest Fourier Transform in the West."
http://www.fftw.org/

OK FFTW is meant to be the best so lets see if we can improve on my last post.

Duv
Your first post was better. We’re going backwards. Have you upgraded to FFT RGB recently? You have missed a couple of stars on the horizontal line but I’m beginning to think there is something fundamentally wrong with byro’s steps. And which I put in my mini tutorial.

Using Alex Chirokov FFT RGB
I very carefully painted out all the stars with a soft brush on a layer mask, changed it back to a selection and used levels to darken to black. The results were not as good as I just got from Image J.
As I said at the beginning my problems started when I ‘Upgraded’ from FFT HSL to FFT RGB.

Flora
Hi, and my apologies. In your picture you had removed the stains etc so I assumed you may have cleaned it further.

If that’s the case then We Are doing something fundamentally wrong Or FFT RGB is not working as well as FFT HSL.

Ken
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