graycoprops (Image Processing Toolbox User's Guide)

Image Processing Toolbox User's Guide

Properties of a gray-level co-occurrence matrix

Syntax

```
stats = graycoprops(glcm, properties)
```

Description

stats = graycoprops(glcm, properties) calculates the statistics specified in properties from the gray-level co-occurence matrix glcm. glcm is an m-by-n-by-p array of valid gray-level co-occurrence matrices. If glcm is an array of GLCMs, stats is an array of statistics for each glcm.

graycoprops normalizes the gray-level co-occurrence matrix (GLCM) so that the sum of its elements is equal to 1. Each element (r,c) in the normalized GLCM is the joint probability occurrence of pixel pairs with a defined spatial relationship having gray level values r and c in the image. graycoprops uses the normalized GLCM to calculate properties.

properties can be a comma-separated list of strings, a cell array containing strings, the string 'all', or a space separated string. The property names can be abbreviated and are not case sensitive.

Property
Description
Formula

'Contrast'
Returns a measure of the intensity contrast between a pixel and its neighbor over the whole image.

Range = [0 (size(GLCM,1)-1)^2]
Contrast is 0 for a constant image.

'Correlation'
Returns a measure of how correlated a pixel is to its neighbor over the whole image.

Range = [-1 1]

Correlation is 1 or -1 for a perfectly positively or negatively correlated image. Correlation is NaN for a constant image.

'Energy'
Returns the sum of squared elements in the GLCM.

Range = [0 1]

Energy is 1 for a constant image.

'Homogeneity'
Returns a value that measures the closeness of the distribution of elements in the GLCM to the GLCM diagonal.

Range = [0 1]

Homogeneity is 1 for a diagonal GLCM.

Property	Description	Formula
`'Contrast'`	Returns a measure of the intensity contrast between a pixel and its neighbor over the whole image. Range = [0 (size(GLCM,1)-1)^2] Contrast is 0 for a constant image.
`'Correlation'`	Returns a measure of how correlated a pixel is to its neighbor over the whole image. `Range = [-1 1]` Correlation is 1 or -1 for a perfectly positively or negatively correlated image. Correlation is `NaN` for a constant image.
`'Energy'`	Returns the sum of squared elements in the GLCM. Range = [0 1] Energy is `1` for a constant image.
`'Homogeneity'`	Returns a value that measures the closeness of the distribution of elements in the GLCM to the GLCM diagonal. Range = [0 1] Homogeneity is 1 for a diagonal GLCM.

stats is a structure with fields that are specified by properties. Each field contains a 1 x p array, where p is the number of gray-level co-occurrence matrices in GLCM. For example, if GLCM is an 8 x 8 x 3 array and properties is 'Energy', then stats is a structure containing the field Energy, which contains a 1 x 3 array.

Notes

Energy is also known as uniformity, uniformity of energy, and angular second moment.

Contrast is also known as variance and inertia.

Class Support

glcm can be logical or numeric, and it must contain real, non-negative, finite, integers. stats is a structure.

Example

GLCM = [0 1 2 3;1 1 2 3;1 0 2 0;0 0 0 3];
stats = graycoprops(GLCM)

I = imread('circuit.tif');
GLCM2 = graycomatrix(I,'Offset',[2 0;0 2]);
stats = graycoprops(GLCM2,{'contrast','homogeneity'})

See Also

graycomatrix

graycomatrix grayslice