public class ErodingSkeleton extends AbstractIterativeArrayProcessor<Matrix<? extends UpdatableBitArray>> implements IterativeArrayProcessor<Matrix<? extends UpdatableBitArray>>
The simplest algorithm of multidimensional skeletonization of binary matrices, based on sequential
erosions
of the matrix by some small pattern.
More precisely, this class is an implementation of IterativeArrayProcessor
interface,
iteratively processing some bit matrix (Matrix
(UpdatableBitArray
)), named
result and passed to the getInstance
method.
In this implementation:
performIteration(ArrayContext)
method
calculates erosion
(result,P) of the current result matrix
by some small pattern P (usually little circle or square, in 2dimensional case) and
opening
(result,Q,Morphology.SubtractionMode.NONE
) of this matrix
by some other pattern Q, usually equal to P or little greater than P.
The opening is subtracted (in the settheoretical sense) from the source result matrix
and the difference (i.e. "thin" areas in the bit image) is united with the erosion
(also in the settheoretical sense).
Then the result matrix is replaced with this union.done()
method returns true if the last iteration was unable to change the matrix:
all "objects" are already "thin" (removed after the erosion).result()
method always returns the reference to the source matrix, passed to
getInstance
method.The algorithm, implemented by this class, does not guarantee that connected "objects" (areas filled by 1 elements) stay connected and does not guarantee that the resulting "skeleton" will be "thin" enough. But it guarantees that resulting "skeleton" does not contain areas "larger" than the pattern Q used for opening operation.
This class is based on Matrices.asShifted
method
with some elementwise logical operations (AND, OR, NOT).
So, the matrix is supposed to be infinitely pseudocyclically continued, as well
Matrices.asShifted
method supposes it.
You can change this behavior by appending the source matrix with zero elements
by calling Matrix.subMatrix(long[], long[], Matrix.ContinuationMode)
Matrix.ContinuationMode.ZERO_CONSTANT
.
This class can process a matrix with any number of dimensions.
This class is not threadsafe, but is threadcompatible and can be synchronized manually, if multithread access is necessary.
context, memoryModel
Modifier and Type  Method and Description 

boolean 
done()
Returns true if and only if the algorithm was successfully finished and there is
no sense to perform further iterations.

long 
estimatedNumberOfIterations()
Estimates the number of iterations, that should be performed from this moment to finish the algorithm.

void 
freeResources(ArrayContext context)
If there are some resources, allocated by this object, which are not controlled
by Java garbage collectors — files, streams, sockets, locks, etc. —
this method tries to release them (for example, to close any files).

static ErodingSkeleton 
getInstance(ArrayContext context,
Matrix<? extends UpdatableBitArray> matrix,
Pattern erosionPattern,
Pattern openingPattern)
Creates new instance of this class.

void 
performIteration(ArrayContext context)
Performs the next iteration of the iterative algorithm.

Matrix<? extends UpdatableBitArray> 
result()
Returns the result of the previous iteration.

java.lang.String 
toString()
Returns a brief string description of this object.

chain, context, limitIterations, part, process
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
chain, limitIterations, process
context
public static ErodingSkeleton getInstance(ArrayContext context, Matrix<? extends UpdatableBitArray> matrix, Pattern erosionPattern, Pattern openingPattern)
context
 the context
that will be used by this object;
may be null, then it will be ignored.matrix
 the bit matrix that should be processed and returned by result()
method.erosionPattern
 the pattern that will be used for erosion operation at every iteration.openingPattern
 the pattern that will be used for opening operation at every iteration.java.lang.NullPointerException
 if one of the arguments is null.public void performIteration(ArrayContext context)
IterativeArrayProcessor
IterativeArrayProcessor.done()
, the results are unspecified:
please never call this method if IterativeArrayProcessor.done()
returns true.
You usually don't need to call this method: please call
IterativeArrayProcessor.process()
instead.
If you need to perform only one or n iterations, you may use
limitIterations(n)
call.
Warning: this method should ignore the current execution context
of this object.
Instead, this method should use the context of execution specified by context argument.
This method is called by IterativeArrayProcessor.process()
method with the argument,
describing a subtrask
of the full algorithm.
The context argument may be null:
this method should work properly in this case (ignore the context).
This method must be implemented while creating a new iterative arrayprocessing algorithm.
performIteration
in interface IterativeArrayProcessor<Matrix<? extends UpdatableBitArray>>
performIteration
in class AbstractIterativeArrayProcessor<Matrix<? extends UpdatableBitArray>>
context
 the context used by this instance for all operations; may be null.public boolean done()
IterativeArrayProcessor
This method usually does not perform actual calculations and works very quickly (just returns and internal flag). However, this condition is not strict.
You usually don't need to call this method: it is automatically called by
IterativeArrayProcessor.process()
method.
This method must be implemented while creating a new iterative arrayprocessing algorithm.
done
in interface IterativeArrayProcessor<Matrix<? extends UpdatableBitArray>>
done
in class AbstractIterativeArrayProcessor<Matrix<? extends UpdatableBitArray>>
public long estimatedNumberOfIterations()
IterativeArrayProcessor
This method may require some time for its execution.
You usually don't need to call this method: it is automatically called from time to time by
IterativeArrayProcessor.process()
method.
It is used for creating subcontexts, describing a part
of the full task.
This method must be implemented while creating a new iterative arrayprocessing algorithm.
estimatedNumberOfIterations
in interface IterativeArrayProcessor<Matrix<? extends UpdatableBitArray>>
estimatedNumberOfIterations
in class AbstractIterativeArrayProcessor<Matrix<? extends UpdatableBitArray>>
public Matrix<? extends UpdatableBitArray> result()
IterativeArrayProcessor
UpdatableArray
or
Matrix
<? extends UpdatableArray
>.
This method returns valid result even if no iterations were performed yet.
If IterativeArrayProcessor.done()
method returns true, the result of this method
is the final result of iterative processing performed by this instance.
This method may return null. In this case, the concrete implementation of this interface should provide additional methods for returning calculation results.
This method does not perform actual calculations and works very quickly.
This method must be implemented while creating a new iterative arrayprocessing algorithm.
result
in interface IterativeArrayProcessor<Matrix<? extends UpdatableBitArray>>
result
in class AbstractIterativeArrayProcessor<Matrix<? extends UpdatableBitArray>>
public void freeResources(ArrayContext context)
IterativeArrayProcessor
Usually, this method just calls
Array.freeResources(context)
and
Matrix.freeResources(context)
for all temporary arrays and matrices, allocated by this object for storing work data.
If IterativeArrayProcessor.result()
method returns AlgART array or matrix (typical situation),
this method calls Array.freeResources(context)
/
Matrix.freeResources(context)
methods
for this array / matrix.
This method may be used in situations when the instance of this object has long time life and will be reused in future.
This method must be implemented while creating a new iterative arrayprocessing algorithm.
freeResources
in interface IterativeArrayProcessor<Matrix<? extends UpdatableBitArray>>
freeResources
in class AbstractIterativeArrayProcessor<Matrix<? extends UpdatableBitArray>>
context
 the context of execution; may be null, then it will be ignored.public java.lang.String toString()
toString
in class java.lang.Object
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