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References: <20020514194122.EQFC25765.rwcrmhc54.attbi.com@rwcrwbc58>
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Message-ID:  <[log in to unmask]>
Date:         Tue, 14 May 2002 14:31:38 -0700
Reply-To:     [log in to unmask]
Sender:       ImageJ Interest Group <[log in to unmask]>
From:         Bob Dougherty <[log in to unmask]>
Organization: OptiNav, Inc.
Subject:      Re: interference filter plugin

Bill,

Hue seems very powerful.  Curved, diffusely reflecting objects can exhibit a
large range of brightness due to Lambert's cosine law, but they seem to stay in
a narrow band of hue. As you say, some collateral selection can occur in remote
objects that accidentally fall in the same hue band.  If you write the plugin,
I'd suggest an option for selecting in HSB space.  Perhaps an HSB ellipsoid
centered on the clicked-upon color, where the H axis is usually narrower than
the S and B axes?   The ColorProcessor method  public void getHSB(byte[] H,
byte[] S, byte[] B) makes it easy to get the data.

Bob


Bill O'Connell wrote:

> Thanks to Bob Dougherty and Joachim Walter for writing a
> very useful plugin. This solution is ideal if the
> regions of interest can be separated purely by hue.
> I had a similar problem in which hue alone was not
> sufficient to separate the regions. I used the following
> solution, which works directly with the RGB image and(I
> think) is implemented in PhotoShop.
> 1) The user clicks on an example pixel of the desired
> color in an RGB image. Say that the pixel has color
> values r,g,b.
> 2) The program finds all pixels within, say, 2 standard
> deviations of r,g, and b, and builds a mask of these
> pixels.
> I implemented this method in a stand alone DELPHI Pascal
> program. If there is sufficient interest, I could write
> it as a plugin.
>
> Bill
> > Javier,
> >
> > Though I haven't done this in ImageJ, I would recommend converting your
> > images from RGB to HSV (Hue, Saturation, Value/lightness,
> > http://www.siggraph.org/education/materials/HyperGraph/color/colorhs.htm).
> > It will then be a fairly simple matter to filter pixels based on Hue value,
> > replacing undesired hue values with the chosen background value.  Then
> > convert back to RGB.
> >
> > Think of it as being analogous to an FFT for color...
> >
> >
> > -BobC
> >
> >
> > -----Original Message-----
> > From: F Javier Diez Guerra [mailto:[log in to unmask]]
> > Sent: Saturday, May 11, 2002 12:59 AM
> > To: [log in to unmask]
> > Subject: interference filter plugin
> >
> > ...
> > So my question:
> > Is there any way (or plugin) of post-processing such images to remove the
> > orange background while maintaining the green signal?
> > ...

--
Robert Dougherty
President, OptiNav, Inc.
(425) 467-1118
[log in to unmask]
http://www.optinav.com

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