set_shape_model_metric — Set the metric of a shape model that was created from XLD contours.
set_shape_model_metric changes the value of the parameter
Metric that was selected during the creation of the shape model
ModelID from XLD contours. For this, the polarity of the model
edges is determined based on the image
Image. The transformation
that maps the model edges to the image position where the respective object
appears is given in
Metric determines the conditions under which the model
is recognized later in the search image. If
'use_polarity', the object in the image and the model must have the
same contrast. If, for example, the model is a bright object on a dark
background, the object is found only if it is also brighter than the
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_shape_model will increase slightly
in this case.
It must be ensured that the object edges in the
Image have the same
(or inverse) polarity as the object edges 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 edges will not
represent the polarity of the object edges during the search. Note that only
the polarity of the edges is determined, not their contrast. Note also that
the polarity is determined from a single-channel image, only. If a
multichannel image is passed in
Image, only the first channel will
be used (and no error message will be returned).
The transformation defined by the matrix
HomMat2D maps the model
contours to the respective position where the object appears in the
Image. It can be obtained by finding the object in the
Image, e.g., with the operator
determining the respective transformation matrix with the procedure
ignores an origin that was set by
set_shape_model_origin and always
assumes (0,0) as the origin. Hence, when finding the object in the
Image, all other operators must have the origin at the point (0,0).
set_shape_model_origin must be called with (0,0) as the
A typical proceeding is to read the XLD contours from file. Since these XLD
contours do not provide polarity information, the shape model must be created
from the XLD contours by setting the parameter
'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 can be determined from the
matching result. To verify the match interactively, the model contours can
be mapped to this position. If the matching result is correct, the value of
Metric can be changed, e.g., to
'use_polarity'. This leads to a faster and more robust recognition
in the following images.
set_shape_model_metric can only be used with shape models that were
created from XLD contours.
This operator modifies the state of the following input parameter:
During execution of this operator, access to the value of this parameter must be synchronized if it is used across multiple threads.
→object (byte / uint2)
Input image used for the determination of the polarity.
ModelID(input_control, state is modified) shape_model
Handle of the model.
Default value: 'use_polarity'
List of values: 'ignore_global_polarity', 'use_polarity'
* * Read the contours from file read_contour_xld_dxf (Contours, 'metal-part-01', , , DxfStatus) * * Scale the contours such that they correspond to the image hom_mat2d_identity (HomMat2DIdentity) hom_mat2d_scale (HomMat2DIdentity, 3.35, 3.35, 0, 0, HomMat2DScale) affine_trans_contour_xld (Contours, ContoursAffineTrans, HomMat2DScale) * * Create the shape model with Metric='ignore_local_polarity' create_shape_model_xld (ContoursAffineTrans, 'auto', rad(0), rad(360), \ 'auto', 'auto', 'ignore_local_polarity', 5, ModelID) * * Get an image of the object and try to find the object in this image read_image (Image, 'metal-parts/metal-parts-01') find_shape_model (Image, ModelID, rad(0), rad(360), 0.5, 1, 0.5, \ 'least_squares', 0, 0.9, Row, Column, Angle, Score) * * Visualize the match vector_angle_to_rigid (0, 0, 0, Row, Column, Angle, HomMat2D) get_shape_model_contours (ModelContours, ModelID, 1) affine_trans_contour_xld (ModelContours, ModelContoursAffineTrans, HomMat2D) * * Set the matching metric to 'use_polarity', based on the position * of the found object set_shape_model_metric (Image, ModelID, HomMat2D, 'use_polarity') * * Use the shape model to detect the object faster and more robust read_image (Image, 'metal-parts/metal-parts-02') find_shape_model (Image, ModelID, rad(0), rad(360), 0.5, 0, 0.5, \ 'least_squares', 0, 0.9, Row, Column, Angle, Score) * * Visualize the matches for Index := 0 to |Score|-1 by 1 vector_angle_to_rigid (0, 0, 0, Row[Index], Column[Index], Angle[Index], \ HomMat2D) affine_trans_contour_xld (ModelContours, ModelContoursAffineTrans, \ HomMat2D) endfor
If the parameters are valid, the operator
returns the value 2 (H_MSG_TRUE). If necessary an exception is raised.