Posted by
Cammer, Michael on
Feb 01, 2011; 1:39pm
URL: http://imagej.273.s1.nabble.com/Making-and-applying-custom-masks-to-FTs-tp3685864p3685866.html
On the power spectrum image, anywhere you draw pixels of zero will be masked and pixels of 255 will be passed. Therefore, you can do thresholding to find peaks or manual drawing. There are examples at
http://rsbweb.nih.gov/ij/docs/menus/process.html#ffthttp://rsbweb.nih.gov/ij/docs/examples/FFT/And this picture was originally a window screen before filtering out the angled vertical lines:
http://www.flickr.com/photos/mcammer/5394773088/-Michael C.
-----Original Message-----
From: ImageJ Interest Group [mailto:
[hidden email]] On Behalf Of Brad Amos
Sent: Tuesday, February 01, 2011 7:56 AM
To:
[hidden email]
Subject: Making and applying custom masks to FTs
I apologise if this message is a repeat: my previous postings were blocked for a while.
I am trying to select parts of the FT of an image and use only these parts in a resynthesised image. I have found examples of this being done with a circular mask, which allows the resynthesis of an image with , in effect, low- or high- pass filtration.
In biological electron microscopy it is often required to find the peaks in the FT, recognizing them as falling on a lattice, and select only these, which results in a low-noise image of ordered structure. The ideal software for doing this would allow the manual input of rectangular boxes of arbitrary size and position, and would allow the recording of the mask , visibly superimposed on the image. To be really convenient, the drawing of a mask anywhere in the FT would force an identical mask to appear symmetrically on the other side of the centre of symmetry of the FT.
Does such a facility exist in Image J? This procedure is extremely useful: as well as reducing noise it allows two different superimposed lattices , arising from a multilayered specimen or the front and back of a helical particle like a virus or microtubule to be separated in the filtered image.
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