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# graycoprops

Properties of 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.

${\sum _{i,j}|i-j|}^{2}p\left(i,j\right)$

'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.

$\sum _{i,j}\frac{\left(i-\mu i\right)\left(j-\mu j\right)p\left(i,j\right)}{{\sigma }_{i}{\sigma }_{j}}$

'Energy'

Returns the sum of squared elements in the GLCM.

`Range = [0 1]`

Energy is 1 for a constant image.

$\sum _{i,j}p{\left(i,j\right)}^{2}$

'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.

$\sum _{i,j}\frac{p\left(i,j\right)}{1+|i-j|}$

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.

## Examples

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