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FFT and Golf Balls

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  #101  
Old 08-21-2005, 11:03 PM
krishna krishna is offline
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Quote:
Originally Posted by deadants
Krishna, did you do the erase centre star technique or the black out the outer stars method? Also are you using a Mac?
I used to do the black out outer stars method and it used to give good results. But your method is much easier and it gives better results (it is doing the blacking out in a different way). In the blacking out method, my experience has been that even after completing, there will be a few patterns left out. To remove them I used to slightly blur the image. But with this method the masking is so complete and the work is over in a few seconds.
Quote:
Originally Posted by deadants
Has anyone else with a Mac tried imageJ, if so which method are you using?
I have been using ImageJ regularly in Mac and have tried in PC also. In PC, I haven't found any difference except sometimes the system hangs. But that cannot be blamed on ImageJ alone.

--
thanks
Krishna.
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  #102  
Old 08-22-2005, 02:33 PM
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Cameraken Cameraken is offline
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Deadants

I tried your method of painting the centre star with white. Painting with white is adding to the FFT. This method does not remove the texture. What it does do is blur the image so that you canít see the texture.

Painting in black removes from the FFT. If your image is going transparent then you must have removed too much.

Post your image and we can work through the steps;

Ken

Last edited by Cameraken; 08-22-2005 at 07:30 PM.
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  #103  
Old 08-23-2005, 07:45 PM
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deadants deadants is offline
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Hi ken,
I wasn't filling the cenre with white, I actually deleted it. But I take your point that the image is being blurred. I have tried several times at blacking out the surronding stars in ImageJ on the Mac but the results are disapointing. The IFFT doesn't seem to do anything, it returns a picture that looks the same as the original.

Here is a link to a good sized halftoned image that we may be able to walk through the process.
http://tinyurl.com/dg3ph
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  #104  
Old 08-24-2005, 12:32 AM
krishna krishna is offline
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I tried the following (see screengrab) and got a sufficiently neat picture. Mid grays get cleared up easily while the pattern on black are persistent.

--
Krishna
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File Type: jpg Original-002-big.jpg (67.6 KB, 35 views)
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  #105  
Old 08-24-2005, 03:16 PM
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Cameraken Cameraken is offline
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Deadants

I have downloaded your picture. It is an image made up entirely of black dots (well crosses) in the white areas and white dots in the dark areas.
If you remove the dots you will remove the entire picture.

FFT is a way of removing Texture. And seeing there is No texture in this photograph I would not even use FFT. However, after saying that the way Krishna has used your method is good.
Yes it is blurring the image but only a little and blurring would be the only way to fill in the dots using any other method.

In photoshop you can achieve the same results with Gaussian blur set at 2 (setting at 3 eliminates even more of the dots but is blurring more)

In my attachment I changed the mode from Indexed to RGB
I used Gaussian blur set at 2 on the face and Gaussian blur set at 3 on the rest.
I think this is slightly better than using ImageJ.

Iíve tried using the same method in FFT RGB and it does not work. So this is specific to ImageJ.


Ken
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File Type: jpg Ken_untitledRGB copy.jpg (86.4 KB, 29 views)

Last edited by Cameraken; 08-24-2005 at 08:14 PM.
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  #106  
Old 08-25-2005, 02:53 AM
krishna krishna is offline
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Quote:
Originally Posted by Cameraken
In my attachment I changed the mode from Indexed to RGB
I used Gaussian blur set at 2 on the face and Gaussian blur set at 3 on the rest.
I think this is slightly better than using ImageJ.

Iíve tried using the same method in FFT RGB and it does not work. So this is specific to ImageJ.
In this case what you say is correct, Ken. But I have come across certain other instances where photos with halftone dots will have to be blurred considerably to get an acceptable picture whereas to the result you get using FFT in ImageJ, you need to add only a slight blur to remove vestiges of pattern.

As you say correctly, both the methods are blurring the image, but may be the algorithms being used (or the methods) might be different and hence the different result.

--
Krishna
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  #107  
Old 08-25-2005, 01:49 PM
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Cameraken Cameraken is offline
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Krishna

I am not very familiar with halftoned images. But I donít think Deadants picture was very representative of what we normally see. You may be right about the way imageJ may blur differently, I donít know.

If you have a picture where you think imageJ has worked better then please post it.


Ken
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  #108  
Old 08-26-2005, 02:50 AM
krishna krishna is offline
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Here is one sample Ken. You can downloade it from
http://www.ola.in/tmp/photo2-sample.jpg

After FFT processing the picutre has been blurred slightly.

--
Krishna

PS: This is a picture scanned from a magazine.
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  #109  
Old 08-26-2005, 03:57 PM
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Cameraken Cameraken is offline
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Krishna

Iíve downloaded your sample Krishna.
Have you scanned this in?
If you have then are you aware of the de-screening options built into the scanner software. I would have thought that you could have got a better scan than this from a magazine.
Try scanning at a much higher resolution than you need, then drop the resolution in PS.
Also try scanning halftones at a 30 degree angle and then straighten up is PS. This can also help.

Anyway, working with what we have got.

This is a halftoned image with a slight texture from the paper it was scanned
The texture could be removed with FFT but I really donít think it would help much as by far the biggest problem is the well spaced halftone dots.

A halftoned image has information missing which is lost forever. Filling in the dots can only be a guess based on the surrounding pixels. So whatever method you use the detail can not be increased.

Here is what I did

Opened the Sample image and cropped it back to the original
Changed mode to RGB
Duplicated the background twice
On BG Copy2 (the top one) Filter > Other > Offset Horizontal=2 OK, Layer Opacity 50%
Select All > Copy Merged > Paste
L1 Filter > Noise > Dust and Scratches 3,3 OK, Layer Opacity 80%
I then used brightness/Contrast and upped the contrast +30
Done.

I suppose you could try Polaroid Dust and Scratches or Neat Image but I donít think you will get much better results.

Krishna. Your results are similar to mine. So unless anyone knows a better way I think a rescan is the only way you will improve on this.

Ken
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File Type: jpg Ken_photo2-sample copy.jpg (76.6 KB, 24 views)
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  #110  
Old 08-27-2005, 01:15 PM
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Craig Walters Craig Walters is offline
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got rid of the 'golf balls', but still have scan lines. just started playing with this FFT stuff. just a bit fussy. one thing i found is, you dont have to split the channels. you can edit the 'stars' in the color image you get after running FFT. and this isnt the FFT RGB one either. run fft, edit the cross marks and lines except the main middle one and then run ifft on that. seems to work just fine.

Craig
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File Type: jpg Image18.jpg (92.0 KB, 34 views)
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