Specify Offset Used in GLCM Calculation
By default, the
graycomatrix function creates a single GLCM, with
the spatial relationship, or offset, defined as two horizontally
adjacent pixels. However, a single GLCM might not be enough to describe the textural
features of the input image. For example, a single horizontal offset might not be
sensitive to texture with a vertical orientation. For this reason,
graycomatrix can create multiple GLCMs for a single input
To create multiple GLCMs, specify an array of offsets to the
graycomatrix function. These offsets define pixel relationships
of varying direction and distance. For example, you can define an array of offsets that
specify four directions (horizontal, vertical, and two diagonals) and four distances. In
this case, the input image is represented by 16 GLCMs. When you calculate statistics
from these GLCMs, you can take the average.
You specify these offsets as a p-by-2 array of integers. Each row
in the array is a two-element vector,
col_offset], that specifies one offset.
row_offset is the number of rows between the pixel of interest
and its neighbor.
col_offset is the number of columns between the
pixel of interest and its neighbor. This example creates an offset that specifies four
directions and four distances for each direction. For more information about specifying
offsets, see the
graycomatrix reference page.
offsets = [ 0 1; 0 2; 0 3; 0 4;... -1 1; -2 2; -3 3; -4 4;... -1 0; -2 0; -3 0; -4 0;... -1 -1; -2 -2; -3 -3; -4 -4];
The figure illustrates the spatial relationships of pixels that are defined by this
array of offsets, where
D represents the distance from the pixel of