I have a image for which I have to calculate the GLCM texture of a selected region. How can I calculate this? I have to calculate the GLCM only for gray area.
To create a Grey-Level Co-occurrence Matrix you simply count how often certain grey Values are Neighbours.
An Example:
Image
1 1 0 2
1 2 2 2
2 2 1 0
Now we define our GLCM as:
GLCM
0 1 2
------------------
0 | (0,0) (0,1) (0,2)
|
1 | (1,0) (1,1) (1,2)
|
2 | (2,0) (2,1) (2,2)
Where (x,y) denotes that how often is the Value y right of the Value x
For our Example we get:
GLCM
0 1 2
------------------
0 | 0 0 1
|
1 | 2 1 1
|
2 | 0 1 3
You can extend this to get more than only the next neighbour or adjust the direction (North, East, South-East etc.) you look for a neighbour if this gives any benefits to your application. You can even create GLCM for every Pixel direction.
After that you can achieve a symmetricall GLCM by counting again but interchanging the position of x and y to get (y,x).
After you have a symmetrical GLCM you can normalize it to get your GLCM Texture.
There is an excellent Paper from Haralick et.al. that you can read: Textural Features for Image Classification.