Simple skeletonisation methods for grids.

Name	Type	Identifier	Description	Constraints
Input
Grid	grid, input	INPUT
Output
Skeleton	grid, output	RESULT
Skeleton	shapes, output, optional	VECTOR
Options
Method	choice	METHOD		Available Choices: [0] Standard [1] Hilditch's Algorithm [2] Channel Skeleton Default: 0
Initialisation	choice	INIT_METHOD	Initialize a grid cell as potential skeleton member based on given threshold.	Available Choices: [0] less than [1] greater than [2] less than or equal [3] greater than or equal Default: 1
Threshold	floating point number	INIT_THRESHOLD		Default: 0.000000
Convergence	integer number	CONVERGENCE		Minimum: 0 Default: 3