set_local_deformable_model_metric — Set the metric of a local deformable model that was created from XLD contours.
set_planar_uncalib_deformable_model_metric changes the value of the parameter Metric that was selected during the creation of the deformable model ModelID from XLD contours. Because no information about the polarity of the model contours is available for XLD contours, the polarity is determined based on a representative Image. For this, the model contours are mapped to the respective position where the object appears in the Image, which is done with the VectorField which must be of the semantic type 'vector_field_absolute' and which can be obtained by a previous call to find_local_deformable_model. Here, the returned VectorField is used for the deformable transformation. Note, that the 'expand_border' option should not be used in find_local_deformable_model, because then the returned VectorField has the wrong image size.
The parameter Metric then determines the conditions under which the model is recognized later in the search image. If Metric = 'use_polarity', the object in the image and the model must have the same contrast. If, e.g., the model is a bright object on a dark background, the object is found only if it is also brighter than the background. If Metric = 'ignore_global_polarity', the object is found in the image also if the contrast reverses globally. In the above example, the object hence is also found if it is darker than the background. The runtime of find_local_deformable_model will increase slightly in this case.
It must be ensured that the object contours in the Image have the same (or inverse) polarity as the object contours in the image in which the object must be searched later. Especially, the object must not be occluded in the Image and the background must be either brighter than the object or darker. Otherwise, the determined polarity of the model contour will not represent the polarity of the object contour during the search. Note that only the polarity of the contours is determined, not their contrast. Note also that the polarity is determined from a single-channel image, only. If a multi-channel image is passed in Image, only the first channel will be used (and no error message will be returned).
A typical proceeding is to read the XLD contours from file. Since these XLD contours do not provide polarity information, the model must be created from the XLD contours by setting the parameter Metric to 'ignore_local_polarity'. Then, in a first search image the model is recognized. The transformation that maps the model contours to the position of the object in the search image is provided in VectorField, which is of the semantic type 'vector_field_absolute'. If the matching result is correct, the value of the parameter Metric can be changed, e.g., to 'use_polarity'. This leads to a faster and more robust recognition in the following images.
set_local_deformable_model_metric can only be used with deformable models that were created from XLD contours.
This operator modifies the state of the following input parameter:
Input image used for the determination of the polarity.
Vector field of the local deformation.
Handle of the model.
Default value: 'use_polarity'
List of values: 'ignore_global_polarity', 'use_polarity'
If the parameters are valid, the operator set_local_deformable_model_metric returns the value 2 (H_MSG_TRUE). If necessary, an exception is raised.