Hi,
you cannot use soft selections for *painting* in the FFT and
the doing the inverse transform.
ImageJ only uses only the white (level 255) or black (level 0)
areas for passing or rejecting. This mask is slightly smoothened
to reduced ringing artifacts (3x3 average, applied 3 times).
Also note that the image displayed as FFT are not the actual
data but a log-scaled version reduced to 8 bits.
What you can do: define the filter as a separate image and use
Process>FFT>Custom Filter...
There is no point in having more than 8-bit resolution for the
filter, ImageJ always converts it to 8 bits.
A value of 255 means "pass", 0 means "block", and in-between
values attenuate image component of the corresponding the
spatial frequency.
Michael
________________________________________________________________
On 21 Aug 2008, at 20:30, NParker wrote:
> Hi there! I'm found out about ImageJ from the RetouchPRO message
> board. It's the only graphic
> application that can handle FFT on the Mac.
>
> So my question is a two-parter:
>
> As I'm sure you know, FFT is a great way to remove repeating
> patterns from an image (like textured
> paper, moire patterns, etc). The method requires using FFT and then
> using a black brush to paint out
> the white "stars" then running Inverse FFT to restore the image.
>
> The painting and airbrush tools in ImageJ are, to be nice, very
> MacPaint circa 1988. Are there any
> anti-aliased, softer or blurry brushes available for it?
>
> It it possible to take my FFT image into Photoshop and do my image
> painting there? When I open my
> Photoshop-painted FFT image into ImageJ and try to run Inverse FFT,
> I get an error that a "Frequency
> Domain image is required".
>
> I'd appreciate any help with this extremely powerful tool.
Locked
