sim_caltab ( : SimImage : CalTabDescrFile, CamParam, CamPose, GreyBackground, GreyCaltab, GreyMarks, ScaleFac : )

Simulate a video image with calibration table.

sim_caltab is used to generate a simulated calibration image. The calibration table description is read from the file CalTabDescrFile and will be projected into the image plane using the given camera parameters (internal camera parameters CamParam and external camera parameters CamPose), see also project_3d_point.

In the simulated image only the calibration table is shown. The image background is set to the grey value GreyBackground, the calibration table background is set to GreyCaltab, and the calibration marks are set to the grey value GreyMarks. The parameter ScaleFac influences the number of supporting points to approximate the elliptic contours of the calibration marks, see also disp_caltab. The increasing of the number of supporting points causes a more accurate determination of the mark boundary, but increases the computation time, too. For each pixel of the simulated video image, which touches such a subpixel-boundary, the grey value is set linearly between GreyMarks and GreyCaltab dependent on the proportion Inside/Outside.

By applying the operator sim_caltab you can generate synthetic calibration images (with known camera parameters!) to test the quality of the calibration algorithm (see camera_calibration).


Parameters

SimImage (output_object)
image -> object : byte
Simulated calibration image.

CalTabDescrFile (input_control)
string -> string
File name of the calibration table description.
Default value: 'caltab.descr'

CamParam (input_control)
number-array -> real / integer
Internal camera parameters.
Number of elements: 8

CamPose (input_control)
number-array -> real / integer
External camera parameters.
Number of elements: 7

GreyBackground (input_control)
integer -> integer
Grey value of image background.
Default value: 128
Suggested values: 0, 32, 64, 96, 128, 160
Restriction: (0 <= GreyBackground) <= 255

GreyCaltab (input_control)
integer -> integer
Grey value of calibration table.
Default value: 224
Suggested values: 144, 160, 176, 192, 208, 224, 240
Restriction: (0 <= GreyCaltab) <= 255

GreyMarks (input_control)
integer -> integer
Grey value of calibration marks.
Default value: 80
Suggested values: 16, 32, 48, 64, 80, 96, 112
Restriction: (0 <= GreyMarks) <= 255

ScaleFac (input_control)
real -> real
Scaling factor to reduce oversampling.
Default value: 1.0
Suggested values: 1.0, 0.5, 0.25, 0.125
Recommended increment: 0.05
Restriction: 1.0 >= ScaleFac


Example
/* read calibration image */
read_image(:Image1:'calib-01.tiff':) >
/* find calibration pattern */
find_caltab(Image1:Caltab1:'caltab.descr',3,112:) >
/* find calibration marks and initial pose */
find_marks_and_pose(Image1,Caltab1::'caltab.descr',
  [0.008,0.0,0.000011,0.000011,384,288,768,576],128,10:
  RCoord1,CCoord1,StartPose1) >
/* read 3D positions of calibration marks */
caltab_points(::'caltab.descr':NX,NY,NZ) >
/* camera calibration */
camera_calibration(::NX,NY,NZ,RCoord1,CCoord1,
  [0.008,0.0,0.000011,0.000011,384,288,768,576],
  StartPose1,11:CamParam,FinalPose,Errors) >
/* simulate calibration image */
sim_caltab(:Image1Sim:'caltab.descr',CamParam,FinalPose,128,224,80,1:).

Result

sim_caltab returns TRUE if all parameter values are correct. If necessary an exception is raised.


Possible Predecessors

camera_calibration, find_marks_and_pose, read_cam_pose, read_cam_par, hom_mat_to_pose


Possible Successors

find_caltab


See also

find_caltab, find_marks_and_pose, camera_calibration, disp_caltab, hom_mat_to_pose, project_3d_point, create_caltab



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