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From: jdm5548@tamsun.tamu.edu (James Darrell McCauley)
Newsgroups: comp.graphics
Subject: texture: "gray-tone spatial dependence matrix - ???"
Keywords: pgm, spatial dependence matrix, algorithm, texture
Message-ID: <13511@helios.TAMU.EDU>
Date: 20 Mar 91 14:35:42 GMT
Sender: usenet@helios.TAMU.EDU
Followup-To: comp.graphics
Organization: Department of Electrical Engineering, Texas A&M University
Lines: 37

I'm not a comp.graphics regular, or even a graphics person, so
bear with me.

I'm trying to write code to find textural features, a la "Textural
Features for Image Classification" by R.M. Haralick, K. Shanmugam, 
and I. Dinstein (IEEE TRANSACTIONS ON SYSTEMS, MAN, AND CYBERNETICS, 
v. SMC-3, No. 6, Nov. 1973). (I'm just starting to learn about 
texture...)

They describe 14 textural features, some of which are: angular second
moment, contrast, correlation, sum of squares (variance), entropy.
These all give a single numeric value describing an image.  To get
these features, is necessary to find what they call a "gray-tone
spatial dependence matrix" (this paper's kind of old, so I'm unsure
of the terminology here).  To quote:

 "Such matrices of gray-tone spatial-dependence frequencies are a
  function of the angular relationship between the neighboring 
  resolution cells as well as a function of the distance between
  them."

Now, I'm hoping that someone knows what I/they mean by "gray-tone
spatial dependence matrix," cause here's the big question:

 Does anyone have an algorithm any code to find this matrix given 
 any angle that is a factor of pi/4 and any distance d?
 
I'm attempting to find the 14 textural features for images in 
PGM format (as in PBMPLUS).  I started writing code to find this
matrix, but the farther I got, the uglier (and longer) it got.
Has anyone already done this?

Thanks,
-- 
James Darrell McCauley (jdm5548@diamond.tamu.edu, jdm5548@tamagen.bitnet)
Spatial Analysis Lab, Department of Agricultural Engineering,
Texas A&M University, College Station, Texas 77843-2117, USA