| Operators |
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 HomMat2D.
The parameter Metric 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, for example, 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_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 find_shape_model and determining the respective transformation matrix with the operator vector_angle_to_rigid.
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 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 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 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_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:
The value of this parameter may not be shared across multiple threads without external synchronization.Input image used for the determination of the polarity.
Handle of the model.
Transformation matrix.
Match metric.
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, ContoursAffinTrans, HomMat2DScale)
*
* Create the shape model with Metric='ignore_local_polarity'
create_shape_model_xld (ContoursAffinTrans, '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 set_shape_model_metric returns the value 2 (H_MSG_TRUE). If necessary an exception is raised.
create_shape_model_xld, create_scaled_shape_model_xld, create_aniso_shape_model_xld
find_shape_model, find_scaled_shape_model, find_aniso_shape_model
create_shape_model_xld, create_scaled_shape_model_xld, create_aniso_shape_model_xld
Matching
| Operators |