Posted by
Michael Schmid on
Apr 07, 2016; 4:29pm
URL: http://imagej.273.s1.nabble.com/version-1-50i-fails-to-save-FFT-as-TIFF-tp5016075p5016080.html
Hi everyone,
just a bit of background information: If you save an FFT as TIFF or ZIP
with the name 'FFT of ...', ImageJ actually saves the raw FFT data that
are hidden behind the 8-bit image that you see (more strictly speaking,
the raw data are a Fast Hartley Transform of the image).
Thus, when loading such an 'FFT of ...' image you can do the back
conversion or any other operations that you are used to do with an FFT.
The 8-bit image that you see will be recovered from the raw FFT data (as
you can do with Process>FFT>Redisplay Power spectrum).
If you save an FFT with a different format or with a different name,
only the 8-bit image that you see gets saved, and the FFT information
will be lost.
The 8-bit image that you see is the power spectrum with logarithmic
scaling of the gray value (usually over several orders of magnitude of
magnitude), with pixel values 1-254 (0 and 255 are reserved for filtering).
Michael
________________________________________________________________
On 2016-04-07 18:02, moreglia wrote:
> Many Thanks, Herbie! You made me realize that the problem was in how I
> converted 32bitRGB to grayscale
> (I used photoshop instead of imageJ). Now that I do the conversion in
> imageJ, the FFT saves as TIFF just fine.
>
> Cheers,
> Mark
--
ImageJ mailing list:
http://imagej.nih.gov/ij/list.html