Operator Reference
create_class_lut_gmm (Operator)
create_class_lut_gmm — Create a look-up table using a gaussian mixture model to classify byte
images.
Signature
create_class_lut_gmm( : : GMMHandle, GenParamName, GenParamValue : ClassLUTHandle)
Description
create_class_lut_gmm generates a look-up table (LUT)
ClassLUTHandle using the data of a trained gaussian mixture model
(GMM) GMMHandle to classify multi-channel byte images. By using
this GMM-based LUT classifier the operator classify_image_class_gmm
of the subsequent classification can be replaced by the operator
classify_image_class_lut. The classification gets a major speed-up,
because the estimation of the class in every image point is no longer
necessary since every possible response of the GMM is stored in the LUT.
For the generation of the LUT, the parameters NumDim,
Preprocessing, and NumComponents defined in the earlier
called operator create_class_gmm are important.
In NumDim, the number of image channels the images must have to be
classified is defined. By using the Preprocessing
(see create_class_gmm) the number of image channels can be
transformed to NumComponents. NumComponents defines
the length of the feature vector, which the classifier
classify_class_gmm handles internally. Because of performance and
disk space, the LUT is restricted to be maximal 3-dimensional. Since
it replaces the operator classify_class_gmm,
NumComponents <= 3 must hold.
If there is no preprocessing that reduces the number of image channels
(NumDim = NumComponents), all possible pixel values,
which can occur in a byte image, are classified with
classify_class_gmm. The returned classes are stored in the LUT.
If there is a preprocessing that reduces the number of image channels
(NumDim > NumComponents), the preprocessing parameters
of the GMM are stored in a separate structure of the LUT. To create the LUT,
all transformed pixel values are classified with classify_class_gmm.
The returned classes are stored in the LUT. Because of the discretization
of the LUT, the accuracy of the LUT classifier could become lower than the
accuracy of classify_image_class_gmm.
With 'bit_depth' and 'class_selection' the accuracy of
the classification, the required storage, and the runtime needed to create
the LUT can be controlled.
The following parameters of the GMM-based LUT classifier can be set with
GenParamName and GenParamValue:
- 'bit_depth':
-
Number of bits used from the pixels. It controls the storage requirement of the LUT classifier and is bounded by the bit depth of the image ('bit_depth' <= 8). If the bit depth of the LUT is smaller ('bit_depth' < 8), the classes of multiple pixel combinations will be mapped to the same LUT entry, which can result in a lower accuracy for the classification. One of these clusters contains pixel combinations, where
NumComponentsdenotes the dimension of the LUT, which is specified increate_class_gmm. For example, for 'bit_depth' = 7,NumComponents= 3, the classes of 8 pixel combinations are mapped in the same LUT entry. The LUT requires at most bytes of storage. For example, forNumComponents= 3, 'bit_depth' = 8 andNumClasses< 16 (specified increate_class_gmm), the LUT requires 8 MB of storage with internal storage optimization. IfNumClasses= 1, the LUT requires only 2 MB of storage by using the full bit depth of the LUT. The runtime for the classification inclassify_image_class_lutbecomes minimal if the LUT fits into the cache. Suggested values: 6,7,8Default: 8
Restriction: 'bit_depth' >= 1, 'bit_depth' <= 8.
- 'class_selection':
-
Method for the class selection for the LUT. Can be modified to control the accuracy and the runtime needed to create the LUT classifier. The value in 'class_selection' is ignored if the bit depth of the LUT is maximal, thus 'bit_depth' = 8 holds. If the bit depth of the LUT is smaller ('bit_depth' < 8), the classes of multiple pixel combinations will be mapped to the same LUT entry. One of these clusters contains pixel combinations, where
NumComponentsdenotes the dimension of the LUT, which is specified increate_class_gmm. By choosing 'class_selection' = 'best', the class that appears most often in the cluster is stored in the LUT. For 'class_selection' = 'fast', only one pixel of the cluster, i.e., the pixel with the smallest value (component-wise), is classified. The returned class is stored in the LUT. In this case, the accuracy of the subsequent classification could become lower. On the other hand, the runtime needed to create the LUT can be reduced, which is proportional to the maximal needed storage of the LUT, which is defined with .List of values: 'fast', 'best'
Default: 'fast'
- 'rejection_threshold':
-
Threshold for the rejection of uncertain classified points of the GMM. The parameter represents a threshold on the K-sigma probability measure returned by the classification (see
classify_class_gmmandevaluate_class_gmm). All pixels having a probability below 'rejection_threshold' are not assigned to any class.Default: 0.0001
Restriction: 'rejection_threshold' >= 0, 'rejection_threshold' <= 1.
Execution Information
- Multithreading type: reentrant (runs in parallel with non-exclusive operators).
- Multithreading scope: global (may be called from any thread).
- Automatically parallelized on internal data level.
This operator returns a handle. Note that the state of an instance of this handle type may be changed by specific operators even though the handle is used as an input parameter by those operators.
Parameters
GMMHandle (input_control) class_gmm → (handle)
GMM handle.
GenParamName (input_control) attribute.name-array → (string)
Names of the generic parameters that can be adjusted for the LUT classifier creation.
Default: []
Suggested values: 'bit_depth', 'class_selection', 'rejection_threshold'
GenParamValue (input_control) attribute.value-array → (string / integer / real)
Values of the generic parameters that can be adjusted for the LUT classifier creation.
Default: []
Suggested values: 8, 7, 6, 'fast', 'best'
ClassLUTHandle (output_control) class_lut → (handle)
Handle of the LUT classifier.
Result
If the parameters are valid, the operator create_class_lut_gmm
returns the value 2 (
H_MSG_TRUE)
. If necessary an exception is raised.
Possible Predecessors
train_class_gmm,
read_class_gmm
Possible Successors
Alternatives
create_class_lut_knn,
create_class_lut_mlp,
create_class_lut_svm
See also
classify_image_class_lut,
clear_class_lut
Module
Foundation