boofcv.alg.geo.calibration

Class RadialDistortionEstimateLinear

java.lang.Object

boofcv.alg.geo.calibration.RadialDistortionEstimateLinear

public class RadialDistortionEstimateLinear
extends java.lang.Object

Estimates radial lens distortion by solving a linear equation with observed features on a calibration grid. Typically used as an initial estimate for use in non-linear optimization. An arbitrary number of distortion parameters can be solved for, but typically only two are found. The estimated is computed using a known intrinsic camera matrix,and homographies relating grid to camera coordinates. Based upon the description found in Section 3.3 in [1].

Radial distortion is modeled using the following equations:
u' = u + (u - u₀)*[ k₁(x² + y²) +k₂(x² + y²)²]
v' = v + (v - v₀)*[ k₁(x² + y²) +k₂(x² + y²)²]
where (u',v') is the observed distortion in pixel coordinates, (u₀,v₀) is the image center in pixel coordinates, (x,y) is the predicted distortion free calibrated coordinates.

The algorithm works by solving the system of equations below:

[ (u-u₀)*r² , (u-u₀)*r⁴ ][k₁] = [u'-u]
[ (v-v₀)*r² , (v-v₀)*r⁴ ][k₂] = [v'-v]

where r² = (x²+y²).

[1] Zhengyou Zhang, "Flexible Camera Calibration By Viewing a Plane From Unknown Orientations," 1999

Constructor Summary

Constructors

Constructor and Description
RadialDistortionEstimateLinear(java.util.List<Point2D_F64> layout, int numParam) Creates a estimator for the specified number of distortion parameters.

Method Summary

Modifier and Type	Method and Description
double[]	getParameters() Returns radial distortion parameters.
void	process(org.ejml.data.DenseMatrix64F cameraCalibration, java.util.List<org.ejml.data.DenseMatrix64F> homographies, java.util.List<CalibrationObservation> observations) Computes radial distortion using a linear method.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RadialDistortionEstimateLinear

public RadialDistortionEstimateLinear(java.util.List<Point2D_F64> layout,
                                      int numParam)

Creates a estimator for the specified number of distortion parameters.

Parameters:

layout - Description of calibration grid

numParam - Number of radial distortion parameters. Two is a good number.

Method Detail

process

public void process(org.ejml.data.DenseMatrix64F cameraCalibration,
                    java.util.List<org.ejml.data.DenseMatrix64F> homographies,
                    java.util.List<CalibrationObservation> observations)

Computes radial distortion using a linear method.

Parameters:

cameraCalibration - Camera calibration matrix. Not modified.

observations - Observations of calibration grid. Not modified.

getParameters

public double[] getParameters()

Returns radial distortion parameters.

Returns:

radial distortion parameters.