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# Image processing GLCM gray level cooccurance matrix

Asked by NA on 5 Mar 2013

In function graycomatrix,the output is always 8x8 matrix,i am not getting why its 8x8 ,can anybody help me out

## Products

Answer by Youssef KHMOU on 5 Mar 2013

hi,

We already discussed that topic , so as to avoid redundancy take a quick look at this topic you will find the answer : http://www.mathworks.com/matlabcentral/answers/64179-what-is-meant-by-glcm-mean-average

Answer by Teja Muppirala on 6 Mar 2013

It's just the default setting. You can change the size by using the 'NumLevels' parameter.

For example,

```I = imread('pout.tif');
G = graycomatrix(I,'NumLevels', 64);
imagesc(G)
```

See the help:

>> help graycomatrix

``` ...
...
...```
```    'NumLevels'      An integer specifying the number of gray levels to use
when scaling the grayscale values in I. For example,
if 'NumLevels' is 8, graycomatrix scales the values in
I so they are integers between 1 and 8.  The number of
gray levels determines the size of the gray-level
co-occurrence matrix (GLCM).```
```                     'NumLevels' must be an integer. 'NumLevels' must be 2
if I is logical.```
```                     Default: 8 for numeric
2 for logical```
``` ...
...
...```