``Hysteresis_Threshold'' -- thresholding using hysteresis

purpose:

Thresholds a grayscale volume using hysteresis, based on a scheme by Canny. Parameters are set manually by the user.

This function will find all objects satisfying the threshold criteria shown below:

1. The object must contain all voxels which satisfy the following relationship.
   
2. All voxels within the object must be connected to above selected voxels and should satisfy the following relationship.
   .
3. The object must be made up of S connected voxels, where S is minimum allowable component size.

Note that and for this function.

input:

An 8-bit grayscale volume.

output:

An 8-bit binary-valued volume.

parameters:

Default parameters menu is

Lower threshold = 100
* Higher threshold = 128
* low threshold tolerance = 5
* high threshold tolerance = 5
* min component size = 10
* connectivity = 6
* connectivity = no_3D;_2D
* input from vol# = 0
* copy output to vol# = 0
*

The ``minimum component size'' parameter sets the value of S described above.
The ``connectivity ='' parameter toggles between 6-- and 26-- connectivity.
The second ``connectivity ='' option toggles between ``no_3D;_2D'' and ``3D;_no_2D'' and specifies how the operation is done. If 2-D option is selected, then:
a) if 6-connectivity is set, then 4-connected 2D analysis is done.
b) if 26-connectivity is set, then 8-connected 2D analysis is done.

comments:

 

1. This function is comparable in run time to the 2-D conn-comp and 3-D conn-comp operations.
2. See Seeded_Hysteresis_Threshold for a comparable function that uses an input seed region to select parameters.