Camera image calibration module.

Collaboration diagram for camCalib:

Camera image calibration module.

Libraries

YARP OpenCV (version >= 2.0) spmap (icub library)

We have enabled changes of the image saturation directly from the rpc port (see port description). This has been done (temporary) in order to change the saturation for the bayer images. The command are sent via rpc can be:

sat 1.0 - no changes in saturation
sat x where x is < 1.0 - will decrease saturation until a gray image is obtained
sat x where x is > 1.0 - will increase saturation

Parameters

Command-line Parameters

The following key-value pairs can be specified as command-line parameters by prefixing -- to the key (e.g. --from file.ini. The value part can be changed to suit your needs; the default values are shown below.

--from camcalib.ini
specifies the configuration file
--context cameraCalibration
specifies the sub-path from $ICUB_ROOT/icub/app to the configuration file
--name camcalib
specifies the name of the module (used to form the stem of module port names)
--group CAMERA_CALIBRATION_LEFT
selects the configuration group to load and, for fisheye rectification, the camera stream to rectify (CAMERA_CALIBRATION_LEFT or CAMERA_CALIBRATION_RIGHT)

Pinhole Lens Calibration

Set projection pinhole in the selected camera calibration group to undistort a standard pinhole camera image. The following parameters are required in that group:

drawCenterCross: 0 to disable or 1 to draw a cross at the principal point
w, h: image size used when deriving the calibration
fx, fy: focal lengths
cx, cy: principal point
k1, k2: radial distortion coefficients
p1, p2: tangential distortion coefficients

The intrinsic matrix is automatically rescaled when the runtime image size differs from w and h. The distortion coefficients remain unchanged.

Example pinhole configuration:

projection pinhole
drawCenterCross 1
w  320
h  240
fx 221.607
fy 221.689
cx 174.29
cy 130.528
k1 -0.397161
k2 0.180303
p1 4.08465e-005
p2 0.000456613

Fisheye Lens Stereo Rectification

The module also supports projection fisheye for stereo fisheye lenses. In this mode, camCalib rectifies one camera stream at a time using the calibration of both cameras plus the stereo extrinsic transform stored in the same configuration file.

Fisheye requirements:

projection fisheye in the selected camera group
--group set to either CAMERA_CALIBRATION_LEFT or CAMERA_CALIBRATION_RIGHT
both [CAMERA_CALIBRATION_LEFT] and [CAMERA_CALIBRATION_RIGHT] groups available
a [STEREO_DISPARITY] group containing HN as a 4x4 homogeneous transform

Each fisheye camera group must contain:

w, h
fx, fy, cx, cy
k1, k2, k3, k4

Fisheye rectification settings:

balance: value in [0,1] controlling the crop level after rectification. It can be specified globally or in the selected camera group; the global value takes precedence.
fovScale: value greater than 0 that scales the output field of view. It can be specified globally or in the selected camera group; the global value takes precedence.
rectifyAlpha: global fallback value for balance when balance is not set.
drawEpipolars: global boolean that overlays horizontal epipolar lines on the rectified image.
epipolarLineStep: global pixel spacing between epipolar lines; values less than one are treated as one.

Fisheye rectification automatically rescales the intrinsic matrices if the runtime image size differs from the calibration size.

Example fisheye configuration:

[CAMERA_CALIBRATION_LEFT]
projection fisheye
w 640
h 480
fx 320.0
fy 320.0
cx 320.0
cy 240.0
k1 -0.01
k2 0.001
k3 0.0
k4 0.0
balance 0.0
fovScale 1.0

[CAMERA_CALIBRATION_RIGHT]
projection fisheye
w 640
h 480
fx 320.0
fy 320.0
cx 320.0
cy 240.0
k1 -0.01
k2 0.001
k3 0.0
k4 0.0

[STEREO_DISPARITY]
HN (-1 0 0 0 0 -1 0 0 0 0 1 0 0.05 0 0 1)

Example invocation:

camCalib –name /icub/camcalib/left –context cameraCalibration –from icubEyes.ini –group CAMERA_CALIBRATION_LEFT

Ports Created

Input port

/camCalib/in
Input image to calibrate (from camera grabber) (rgb)

Output port

/camCalib/out
Calibrated output image (rgb)

Rpc port

/camCalib/conf
Rpc port to change the output image saturation used primarely for the bayer images

Configuration Files

camcalib.ini in $ICUB_ROOT/app/cameraCalibration

Tested OS

Linux: Ubuntu 9.10, Debian Stable, squeeze and windows

Example Instantiation of the Module

camCalib –name /icub/camcalib/left –context cameraCalibration –from icubEyes.ini –group CAMERA_CALIBRATION_LEFT

More information on camera calibration:
OpenCV: http://opencvlibrary.sourceforge.net/CvReference#cv_3d
Matlab Toolbox: http://www.vision.caltech.edu/bouguetj/calib_doc/

See also: CamCalibModule; CalibTool

Author: Lijin Aryananda, Jonas Ruesch

Libraries

YARP OpenCV (version >= 2.0) spmap (icub library)

We have enabled changes of the image saturation directly from the rpc port (see port description). This has been done (temporary) in order to change the saturation for the bayer images. The command are sent via rpc can be:

sat 1.0 - no changes in saturation
sat x where x is < 1.0 - will decrease saturation until a gray image is obtained
sat x where x is > 1.0 - will increase saturation

Parameters

Command-line Parameters

The following key-value pairs can be specified as command-line parameters by prefixing -- to the key (e.g. --from file.ini. The value part can be changed to suit your needs; the default values are shown below.

--from camcalib.ini
specifies the configuration file
--context cameraCalibration
specifies the sub-path from $ICUB_ROOT/icub/app to the configuration file
--name camcalib
specifies the name of the module (used to form the stem of module port names) For calibration configuration options see: PinholeCalibTool::configure

Configuration File Parameters

The following key-value pairs can be specified as parameters in the configuration file The value part can be changed to suit your needs; the default values are shown below.

projection pinhole
drawCenterCross 1
w  320
h  240
fx 221.607
fy 221.689
cx 174.29
cy 130.528
k1 -0.397161
k2 0.180303
p1 4.08465e-005
p2 0.000456613

Ports Created

Input port

/camCalib/in
Input image to calibrate (from camera grabber) (rgb)

Output port

/camCalib/out
Calibrated output image (rgb)

Rpc port

/camCalib/conf
Rpc port to change the output image saturation used primarely for the bayer images

Configuration Files

camcalib.ini in $ICUB_ROOT/app/cameraCalibration

Tested OS

Linux: Ubuntu 9.10, Debian Stable, squeeze and windows

Example Instantiation of the Module

camCalib –name /icub/camcalib/left –context cameraCalibration –from icubEyes.ini –group CAMERA_CALIBRATION_LEFT

More information on camera calibration:
OpenCV: http://opencvlibrary.sourceforge.net/CvReference#cv_3d
Matlab Toolbox: http://www.vision.caltech.edu/bouguetj/calib_doc/

See also: CamCalibModule; CalibTool

Author: Lijin Aryananda, Jonas Ruesch