🚀 go-pugleaf

In article <9209011949.AA19843@hp-and.an.hp.com>, susanm@hp-and.an.hp.com (Susan Margulies) writes:
...
> Basically, I am trying to come up with a way of visualizing the
> phase information as a function of position.  I am already
> displaying the magnitude information by mapping transform
> coefficients into grey scale information.  But since it is the phase
> --
> Susan E. Margulies       
> HP Imaging Systems       
> 508-681-2153 (work)      
> susanm@hp-and.an.hp.com  


A couple of folks have responded with suggestions regarding using hue and
luminance (or value if you talk HSV) to show the two parameters.  We have
been working on multiparameter visualizations as applied to medical image
display (for instance showing metabolic and anatomic information in a single
image as opposed to two separate images).  The primary method I have
investigated for doing this is similar to what the other folks have
suggested, that being, using hue to encode one dimension and luminance the
other dimension.  This can be fairly easily done on standard unix
workstations (with 8 bit color, or better yet deeper framebuffers).  The
following is a summary of advice based on our current (limited) experience.

1) Do the lower frequencey signal with hue and the higher frequency signal with
luminance (humans don't perceive high frequency hue changes very
quantatively).  

2) Don't use low level luminance values (because you can't distinguish hues at
near black)

3) Provide interactive control.  For instance we allow the users to threshold
from 0-100% the hue mapping and 0-100% of the luminance mapping.  This
allows them to "fade" either dimension in and out.

4) A hue range from Red to Green works fairly well for a lot of visual
system reasons.  Avoid crossing over several different major colors (ie. no
rainbow hue attempts).  We are fairly picky on our choices (I use a
perceptually linear greyscale base on the luminance side, and at each a
luminance scale step a peceptually linear hue scale between two hues on the
hue side.  Note that you want to be careful in your hue choice offerings and
to offer some altervatives (as we were reminded by a couple of our RG
"colorblind" observers).

-Brad Hemminger
bmh@rad.unc.edu
Dept of Radiology
Medical Image Display Research Lab
University of North Carolina at Chapel Hill