Operator Reference
image_points_to_world_plane (Operator)
image_points_to_world_plane — Transform image points into the plane z=0 of a world coordinate system.
Signature
Description
The operator image_points_to_world_plane transforms image points
which are given in Rows and Cols into the plane z=0 in a
world coordinate system and returns their 3D coordinates in X and
Y. The world coordinate system is chosen by passing its pose
relative to the camera coordinate system in WorldPose.
Hence, latter one is expected in the form
, where
ccs denotes the camera coordinate system and
wcs the world coordinate system (see
Transformations / Poses
and “Solution Guide III-C - 3D Vision”).
In CameraParam you must pass the internal camera parameters
(see Calibration for the sequence of the parameters
and the underlying camera model).
In many cases CameraParam and WorldPose are the result of
calibrating the camera with the operator calibrate_cameras. See
below for an example.
With the parameter Scale you can scale the resulting 3D coordinates.
The parameter Scale must be specified as the ratio desired
unit/original unit. The original unit is determined by the coordinates of
the calibration object. If the original unit is meters (which is the case if
you use the standard calibration plate), you can set the desired unit
directly by selecting 'm', 'cm', 'mm' or
'um' for the parameter Scale.
Internally, the operator first computes the line of sight between the
projection center and the image contour points in the camera coordinate
system, taking into account the radial distortions. The line of sight is
then transformed into the world coordinate system specified in
WorldPose. By intersecting the plane z=0 with the line of sight the
3D coordinates X and Y are obtained.
It is recommended to use only those image points Rows and
Cols, that lie within the calibrated image size. The mathematical
model does only work well for image points, that lie within the calibration
range.
Execution Information
- Multithreading type: reentrant (runs in parallel with non-exclusive operators).
- Multithreading scope: global (may be called from any thread).
- Processed without parallelization.
Parameters
CameraParam (input_control) campar → (real / integer / string)
Internal camera parameters.
WorldPose (input_control) pose → (real / integer)
3D pose of the world coordinate system in camera coordinates.
Number of elements: 7
Rows (input_control) coordinates.y-array → (real / integer)
Row coordinates of the points to be transformed.
Default: 100.0
Cols (input_control) coordinates.x-array → (real / integer)
Column coordinates of the points to be transformed.
Default: 100.0
Scale (input_control) number → (string / integer / real)
Scale or dimension
Default: 'm'
Suggested values: 'm', 'cm', 'mm', 'microns', 'um', 1.0, 0.01, 0.001, 1.0e-6, 0.0254, 0.3048, 0.9144
Restriction:
Scale > 0
X (output_control) coordinates.x-array → (real)
X coordinates of the points in the world coordinate system.
Y (output_control) coordinates.y-array → (real)
Y coordinates of the points in the world coordinate system.
Example (HDevelop)
* Perform camera calibration (with standard calibration plate).
calibrate_cameras (CalibDataID, Error)
get_calib_data (CalibDataID, 'camera', 0, 'params', CamParam)
* Get reference pose (pose 2 of calibration object 0).
get_calib_data (CalibDataID, 'calib_obj_pose',\
[0,2], 'pose', WorldPose)
* Compensate thickness of plate.
set_origin_pose(ObjInCameraPose, 0, 0, 0.0006, WorldPose)
* Transform image points into world coordinate system (unit mm).
image_points_to_world_plane(CamParam, WorldPose, PointRows, PointColumns, \
'mm', PointXCoord, PointYCoord)
Result
image_points_to_world_plane returns 2 (
H_MSG_TRUE)
if all parameter values
are correct. If necessary, an exception is raised.
Possible Predecessors
create_pose,
hom_mat3d_to_pose,
camera_calibration,
hand_eye_calibration,
set_origin_pose
See also
contour_to_world_plane_xld,
project_3d_point
Module
Calibration