No absolute answer possible Depends on what you intend to mean
by a small or large distance between images. If you wish to measure distances as
human eye might see them then you might want to transform the intensities so
that there is less difference between levels of gray that humans have
difficulty distinguishing (darker shades of gray).
----------------------
F. James Rohlf, Distinguished Professor
Dept. Ecology and Evolution, Stony Brook University, NY
11794-5245
From: Classification,
clustering, and phylogeny estimation [mailto:[log in to unmask]] On
Behalf Of Yakir Gagnon
Sent: Friday, May 14, 2010 11:35 AM
To: [log in to unmask]
Subject: A good measure of distance for pixel intensities
Hi!
Background: I want to compare two images that are identical in many
respects (pixel-wise) but are different in the pixel intensity values they
have. I'm aware of the many image comparison methods out there, but I want to
keep it very very simple (for all the image analysists: these two
images are artificial and made through the same process with some differences
without any spatial translation).
What I am doing right now: is calculating
the euclidian distance between the pixel intensities of the 2 images. The
mean of all the distances (if the image is 500*500 pixels then there are 500^2
distances) gives me a measure of how similar those images are.
My question is: is the euclidian distance
really the best option when comparing natural numbers that can only range
between 0 and 255, or should I use some other measure of distance or transform
the pixel intensities first?
Thanks in advance!
Yakir L. Gagnon, PhD student
The Lund Vision Group
Tel +46 (046) 222 93 40
Cell +46 (073) 753 63 54
Fax +46 (046) 222 44 25
http://www.lu.se/o.o.i.s/7758
http://www.google.com/profiles/12.yakir
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