Re: Editing the FFT of a jpeg

Posted by Joel Sheffield on Sep 18, 2009; 10:57pm
URL: http://imagej.273.s1.nabble.com/Editing-the-FFT-of-a-jpeg-tp3691067p3691074.html

I generally set the foreground to black --you have to be sure that your
black is truly black (value 0).  I then select the area, as you do, and fill
the area (ctl-f).  I have found that if I have been working in an RGB world,
sometimes the black isn't true black, and then there are problems.

Joel


On Fri, Sep 18, 2009 at 6:02 PM, Robby Connor
<[hidden email]>wrote:

> I am trying to load an jpeg into ImageJ and run an FFT on it to edit out a
> known pattern I have.  The problem I am having is after I edit the
> transformed image and inverse FFT nothing has changed.  I can tell my edit
> has no effect because I can black out the entire frequency-domain picture
> and run an inverse FFT on it, which will result in my exact same original
> picture.
>
> The weirdest thing about this is that it actually worked for about 2 days
> on
> one of my computers, then stopped working (it never worked on the other
> computer).  When it was working, here were my steps:
> 1)convert to 8-bit black and white under Image>>Type.
> 2)change my editing background paint color to black.
> 3)run the Process>>FFT>>FFT on the picture.
> 4)select circular areas on the transformed picture relating to the
> frequencies of the grid pattern of the original, then press backspace.
>  This
> deleted the area and left a black color due to step 2).
> 5)run the Process>>FFT>>Inverse FFT.
>
> This had been working, then spontaneously stopped working.  I had been
> trying to check if any settings were different from the computer whose
> ImageJ Inverse FFT worked to the one that didn't, so I could've
> accidentally
> changed something critical.
>
> MAIN QUESTION:
> How do I get this feature to work again?
>
> SECONDARY QUESTION:
> Is there any other program (or an add-on to ImageJ) that anybody knows
> about
> that would do this process for me?
>
> EXTRA INFO:
> I run XP on both computers.
>

--


Joel B. Sheffield, Ph.D
Department of Biology
Temple University
Philadelphia, PA 19122
Voice: 215 204 8839
e-mail: [hidden email]
URL:  http://astro.temple.edu/~jbs