Operators

# cooc_feature_matrix (Operator)

## Name

cooc_feature_matrix — Calculate gray value features from a co-occurrence matrix.

## Signature

cooc_feature_matrix(CoocMatrix : : : Energy, Correlation, Homogeneity, Contrast)

## Description

The operator calculates from a co-occurence matrix (CoocMatrix) the energy (Energy), correlation (Correlation), local homogeneity (Homogeneity) and contrast (Contrast).

The operator cooc_feature_matrix calculates the gray value features from the part of the input matrix generated by gen_cooc_matrix corresponding to the direction matrix indicated by the parameters LdGray and Direction according to the following formulae:

```  Energy:
width   width
----    ----
\       \
Energy  =       /       /     cij  *  cij
----    ----
i=0     j=0

(Measure for image homogeneity)

Correlation:
width  width
----   ----
\      \
/      /      (i - ux) * (j - uy) * cij
----   ----
i=0    j=0
Correlation  =  -----------------------------------------
sx  *  sy

(Measure for gray value dependencies)

Local homogeneity:

width  width
----   ----
\      \            1
Homogeneity  =  /      /      ------------- * cij
----   ----   1 + (i - j)^2
i=0    j=0

Contrast:

width   width
----    ----
\       \
Contrast  =     /       /     (i - j)^2  *  cij
----    ----
i=0     j=0

(Measure for the size of the intensity differences)

where

width           2^LdGray - 1

cij             Entry of co-occurrence matrix

width   width
----    ----
\       \
ux              /       /     i  *  cij
----    ----
i=0     j=0

width   width
----    ----
\       \
uy              /       /     j  *  cij
----    ----
i=0     j=0

width   width
----    ----
\       \
sx^2            /       /     (i - ux)^2  * cij
----    ----
i=0     j=0

width   width
----    ----
\       \
sy^2            /       /     (i - uy)^2  *  cij
----    ----
i=0     j=0
```

## Attention

The region of the input image is disregarded.

## Parallelization

• Multithreading type: reentrant (runs in parallel with non-exclusive operators).
• Automatically parallelized on tuple level.

## Parameters

CoocMatrix (input_object)  singlechannelimage(-array) object (real)

Co-occurrence matrix.

Energy (output_control)  real (real)

Homogeneity of the gray values.

Correlation (output_control)  real (real)

Correlation of gray values.

Homogeneity (output_control)  real (real)

Local homogeneity of gray values.

Contrast (output_control)  real (real)

Gray value contrast.

## Result

The operator cooc_feature_matrix returns the value 2 (H_MSG_TRUE) if an image with defined gray values is passed and the parameters are correct. The behavior in case of empty input (no input images available) is set via the operator set_system(::'no_object_result',<Result>:). If necessary an exception is raised.