| Operators |
find_calib_object — Find the HALCON calibration plate and set the extracted points and contours in a calibration data model.
find_calib_object(Image : : CalibDataID, CameraIdx, CalibObjIdx, CalibObjPoseIdx, GenParamName, GenParamValue : )
find_calib_object searches in Image for a HALCON calibration plate corresponding to the description of the calibration object with the index CalibObjIdx from the calibration data model CalibDataID. If a calibration plate is found, find_calib_object extracts the centers and the contours of its marks and estimates the pose of the plate relative to the observing camera CameraIdx. All collected observation data is stored in the calibration data model for the calibration object pose CalibObjPoseIdx. In order to ensure a successful detection of the calibration plate, the entire calibration plate has to be visible in the image if calibration plates with rectangularly arranged marks are used, whereas it is sufficient for calibration plates with hexagonally arranged marks if at least one of the finder pattern is completely visible.
Before the operator find_calib_object can be called, a calibration data model has to be defined performing the following steps:
Create a calibration data model with the operator create_calib_data, specifying the number of cameras in the setup and the number of used calibration objects.
Specify the camera type and the initial internal camera parameters for all cameras with the operator set_calib_data_cam_param. Note that only cameras of the same type can be calibrated in a single setup.
Specify the description of all calibration objects with the operator set_calib_data_calib_object. Note that for a successful call of find_calib_object a valid description file of the calibration plate is necessary. This description file has to be set beforehand via the operator set_calib_data_calib_object. As a consequence, the usage of a user-defined calibration object can only be made by the operator set_calib_data_observ_points.
find_calib_object is used to collect observations in a calibration data model. Beyond, it stores additional observation data that cannot be added to the model with set_calib_data_observ_points and that is dependent on the used calibration plate. While for calibration plates with rectangularly arranged marks (see gen_caltab) the rim of the calibration plate is added to the observations, calibration plates with hexagonal pattern (see create_caltab) store one of their finder pattern. Additionally and irrespective of the used calibration plate, the contour of each mark is added to the calibration model.
Using calibration plates with hexagonally arranged marks, the following additional parameter can be set via GenParamName and GenParamValue:
Smoothing factor for the extraction of the mark contours. For increasing values of 'sigma', the filter width and thereby the amount of smoothing increases (see also edges_sub_pix for the influence of the filter width on the Canny filter).
Suggested values: 0.5, 0.7, 0.9, 1.0 (default), 1.2, 1.5
For calibration plates with rectangularly arranged marks, find_calib_object essentially encapsulates the sequence of three operator calls: find_caltab, find_marks_and_pose and set_calib_data_observ_points. For this kind of calibration plates the following parameters can be set using GenParamName and GenParamValue:
Smoothing factor for the extraction of the mark contours. For increasing values of 'alpha', the filter width and thereby the amount of smoothing decreases (see also edges_sub_pix for the influence of the filter width on the Lanser2 filter ).
Suggested values: 0.5, 0.7, 0.9 (default), 1.0, 1.2, 1.5
Tolerance factor for gaps between the marks. If the marks appear closer to each other than expected, you might set 'gap_tolerance' < 1.0 to avoid disturbing patterns outside the calibration plate to be associated with the calibration plate. This can typically happen if the plate is strongly tilted and positioned in front of a background that exposes mark-like patterns. If the distances between single marks vary in a wide range, e.g., if the calibration plate appears with strong perspective distortion in the image, you might set 'gap_tolerance' > 1.0 to enforce the marks grouping (see also find_caltab).
Suggested values: 0.75, 0.9, 1.0 (default), 1.1, 1.2, 1.5
Maximum expected diameter of the marks (needed internally by find_marks_and_pose). By default, this value is estimated by the preceding internal call to find_caltab. However, if the estimation is erroneous for no obvious reason or the internal call to find_caltab fails or is simply skipped (see 'skip_find_caltab' below), you might have to adjust this value.
Suggested values: 50.0, 100.0, 150.0, 200.0, 300.0
Skip the internal call to find_caltab. If activated, only the domain of Image reduces the search area for the internal call of find_marks_and_pose. Thus, a user defined calibration plate region can be incorporated by setting 'skip_find_caltab'='false' and reducing the Image domain to the user region.
List of values: 'false' (default), 'true'
If using a HALCON calibration plate as calibration object, it is recommended to use find_calib_object instead of set_calib_data_observ_points where possible, since the contour information, which it stores in the calibration data model, enables a more precise calibration procedure with calibrate_cameras.
After a successful call to find_calib_object, the extracted points can be queried by get_calib_data_observ_points and the extracted contours can be accessed by get_calib_data_observ_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.
Handle of a calibration data model.
Index of the observing camera.
Default value: 0
Suggested values: 0, 1, 2
Index of the calibration object.
Default value: 0
Suggested values: 0, 1, 2
Index of the observed calibration object.
Default value: 0
Suggested values: 0, 1, 2
Restriction: CalibObjPoseIdx >= 0
Names of the generic parameters to be set.
Default value: []
List of values: 'alpha', 'gap_tolerance', 'max_diam_marks', 'sigma', 'skip_find_caltab'
Values of the generic parameters to be set.
Default value: []
Suggested values: 0.5, 0.9, 1.0, 1.2, 1.5, 2.0, 'true', 'false'
read_image, find_marks_and_pose, set_calib_data_cam_param, set_calib_data_calib_object
set_calib_data, calibrate_cameras
find_caltab, find_marks_and_pose, set_calib_data_observ_points
Calibration
| Operators |