[lug] Looking for image manipulation software

[Ed Hill]

On Tue, 2004-11-23 at 19:55 -0700, Paul E Condon wrote:
> I'm looking for a software package that will allow me to overlay and subtract one
> image from another. Perhaps, all I need is help getting gimp to do what I want.
> 
> By subtract, I mean pixel-by-pixel difference of pixel values so that if the two
> input images are identical, the result is an blank image. I can get two images overlaid.
> I can move one relative to another, and if I spent another few hours looking I might
> find a way to input x,y shifts as number of pixels rather than using the mouse to
> drag and drop. But even when I do get them overlaid with the mouse, that only increases
> the contrast of the image. Choosing modes subtract or difference doesn't help.
> 
> Is there some other software that is more oriented towards images as data rather than
> images as graphic art?


Hi Paul,

The operation that you seem to be describing is called "image
registration" and its the process of translating, rotating, and/or
stretching one image to get it to (in some sense) align with a second
image.  This sort of thing is done frequently in the medical imaging
business.

There are many programs or software toolkits that can either do some
kind of image registration or can be used as a programming framework
within which you can write your own image analysis routines.  Heres a
sample, and you can Google for more:

 Free:  Octave, ITK, ImageMagick
 Commercial:  MatLAB, IDL

While its not cheap, it is very easy to write all sorts of image
analysis routines in MatLAB.  In fact, I wrote an image registration
script in just a few lines of MatLAB code last year as part of a dyed
tracer dispersion project.

Octave is basically a Free clone of MatLAB and it also provides numerous
image handling routines:

  http://octave.sourceforge.net/index/image.html

Ed


-- 
Edward H. Hill III, PhD
office:  MIT Dept. of EAPS;  Rm 54-1424;  77 Massachusetts Ave.
             Cambridge, MA 02139-4307
emails:  eh3 at mit.edu                ed at eh3.com
URLs:    http://web.mit.edu/eh3/    http://eh3.com/
phone:   617-253-0098
fax:     617-253-4464