__header__

Description

Radial distortion
This fit an distortion of type barrel or pin cushion and is of the form

         pixel undistorted = pixel distorted(k0 + k1*r + k2*r*r + k3*r*r*r + k4*r*r*r*r)

the model can be made to work on any lines present in and image although the current tool uses a presented grid pattern

We are only considering radial not tangential - as the later is said to be neglegable
Best result at typically found by having the software calculate the even terms k2 amd k4 and this line up with Optical theory which shows that this polynomial should only feature even powers. However many graphic packages seem to use k1 and k3 (adobe? and image magick)

k0 typical is set to 1-k1-k2-k3-k4 (in normalized coordiantes this preserves size)

Based on the papers
Straight Lines Have to Be Straight
Automatic Calibration and Removal of Distortion from Scenes of Structured Environments
Frederic Devernay, Olivier Faugeras


Correcting Lens Distortions in Digital Photographs
Wolfgang Hugemann

the system works in normalized coordinates
so determine the centre and skew factor as well as the radial k1 and k2....;
x_undistorted = S * x_Distorted + Center_x
y_undistorted = y_Distorted + Center_y

These are reported.



NOTE the revert (inverse) has two option

Inputs

CIFViewer

NOt used

CalibrationCollection

PointsImage

Points of a grid (straght lines ust be straight)

Parameters

Name

GridSizeX
GridSizeY

for a polynomial distortion fit is the distance between the points
effectively this does distortion and spacial calibration.

for a radial distortion the point a assumed to be sorted into a grid. Strictly this should not be necessary.

MaxErrorPre
SDErrorPre

error pre fit

MaxErrorPost
SDErrorPost

error post fit

Calibration

RadialImageWidth
RadialImageHeight

Image size - only the smaller is used

RadialOptions

Radial|Radial And Center|Radial And Center And Aspect
Aspect/Skew is questionaable??

RadialK1
RadialK2
RadialK3
RadialK4

Which radial k terms to evaluate. Recommend k2 and k4 __footer__