| Re: Image subtraction [message #11635] |
Thu, 21 May 1998 00:00  |
pford
Messages: 33
Registered: September 1996
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Member |
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Try
tvscl, image1 - A * image2
where A is a correction factor for intensity. One of the problems here is
how are negative numbers handled, should you change the images to float
to allow non integer As, and what value should A be, see? (I could not
resist the pun.)
To set values less than 0 to 0, you could use one of those matrix logical
something like: img = img * (img GE 0.0)
(I don't have the ref material handy and unlike many here, I need to
lookup all but the simplest of stuff.)
For A, there are many ways to determine a value, such as the average of
the images ratio, max ratio, etc. Or the one I commonly use, trial and
error.
You could always write(e-mail) the author of NIH Image to find out what he
is
doing, whose name escapes me. He
usually is fairly responsive, or you could examine the sourse code that,
at least in the past, was available.
BTW, is NIH image still just a Mac program?
Patrick Ford, MD
Baylor College of Medicine
pford@bcm.tmc.edu
FRANCOIS LAROSE (aah904@agora.ulaval.ca) wrote:
: Ok,
: Let me explain, I take two gray scale images and subtract them togethers.
: Then, I display the result on screen with TVSCL command. When I say, I get
: poor
: result, is because I compare the result of this subtraction with the
: result
: of a program that make image subtraction (NIH image). The two are very
: different. So, I suppose I should do something else to get the same
: result.
: For the package, I working in research so I can't afford a expensive one.
: Maybe, you can point me some web site...
: Tanks
: Frank
: At 09:59 18/05/98 -0600, you wrote:
: >you writes:
: >
: >> I need to do some image subtraction. With IDL, if I only do
: >> Image1 - image2 and I get poor result. Does it have best code to
: >> do image subtraction?
: >
: >Poor result how? Can't see it? Doesn't look like what
: >you expect? Don't believe the results?
: >
: >Try this:
: >
: > TV, BytScl(image1 - image2, top=!D.N_Colors-1)
: >
: >Does that help?
: >
: >> PS If you know a good package of image analisys in IDL, just let me
: know!
: >
: >How much would you be willing to pay for this? :-)
: >
: >David
: >
: >-----------------------------------------------------------
: >David Fanning, Ph.D.
: >Fanning Software Consulting
: >E-Mail: davidf@dfanning.com
: >Phone: 970-221-0438
: >Coyote's Guide to IDL Programming: http://www.dfanning.com/
: >
: >
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