Posted by
Michael Schmid on
Mar 16, 2010; 10:05am
URL: http://imagej.273.s1.nabble.com/Trouble-running-Custom-filter-from-plugin-tp3688954p3688955.html
Hi Neil,
just to make sure there are no misunderstandings:
Process>FFT>Custom Filter is in the Fourier domain, with low
frequencies at the center. So, your filter is actually a high-pass
filter.
The filter should have values of 255 for the frequencies that should
pass unattanuated.
If you want a convolution operation, use Process>Filters>Convolve.
You will need a kernel size that is an odd number (e.g., 3x3, 5x5;
you can also have 1D kernels like 1x7 or 7x1).
Michael
________________________________________________________________
On 15 Mar 2010, at 23:34, ph73nt wrote:
> Hi list,
>
> I'm not getting the results I expect when I call the "Custom
> Filter..." menu
> command from a plugin. I'm writing a plugin that iteratively
> applies a
> custom filter to a series of small pixel blocks of the input
> image. All
> images are 32 bit floats. Here is a schematic of the steps I take:
>
> - Create a filter image block, a 4x4px imageplus (imFilter) in a
> window
> titled "Filter"
> - For simple testing I'm using a filter where the values are unity
> at the
> edges and zero elsewhere:
> 1 1 1 1
> 1 0 0 1
> 1 0 0 1
> 1 1 1 1
> - I create a new image from the original image (imp) to form my
> current
> "block" (imBlock), again a 4x4 square image block
> - For testing I'm forcing the values in this block to have known
> values:
> 0 1 2 3
> 0 0 0 0
> 4 5 6 7
> 0 0 0 0
> - I use "Custom Filter..." to filter imBlock with imFilter.
>
> If I do the Custom Filter manually by using the menus I get an
> image block
> that appears smoothed, which I'm expecting. But if I try to
> automate this
> in my plugin, the image block ends up as just a 4x4 image with zero-
> valued
> pixels everywhere.
>
> The command I'm using to call the filter is:
> ij.IJ.run(imBlock, "Custom Filter...", "filter=[Filter]");
>
> Is there something implicitly wrong with the way I am calling the
> filter?
> Any suggestions/criticisms would be gratefully received.
>
> Many thanks, Neil
>
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