CalibrationPatternExtractCalibrationLists Method (ImagePlane, CalibrationPatternStyle, CalibrationPatternContrast, Int32, Int32, Double, Point2Dd, Point2Dd)

public static void ExtractCalibrationLists(
	ImagePlane plane,
	CalibrationPatternStyle style,
	CalibrationPatternContrast contrast,
	int gridSpacing,
	int minContrast,
	double maxRatio,
	out Point2Dd[] originalPixels,
	out Point2Dd[] transformedPixels
)

Public Shared Sub ExtractCalibrationLists ( 
	plane As ImagePlane,
	style As CalibrationPatternStyle,
	contrast As CalibrationPatternContrast,
	gridSpacing As Integer,
	minContrast As Integer,
	maxRatio As Double,
	<OutAttribute> ByRef originalPixels As Point2Dd(),
	<OutAttribute> ByRef transformedPixels As Point2Dd()
)

public:
static void ExtractCalibrationLists(
	ImagePlane plane, 
	CalibrationPatternStyle style, 
	CalibrationPatternContrast contrast, 
	int gridSpacing, 
	int minContrast, 
	double maxRatio, 
	[OutAttribute] array<Point2Dd>^% originalPixels, 
	[OutAttribute] array<Point2Dd>^% transformedPixels
)

static member ExtractCalibrationLists : 
        plane : ImagePlane * 
        style : CalibrationPatternStyle * 
        contrast : CalibrationPatternContrast * 
        gridSpacing : int * 
        minContrast : int * 
        maxRatio : float * 
        originalPixels : Point2Dd[] byref * 
        transformedPixels : Point2Dd[] byref -> unit 

Parameters

plane

Type: Stemmer.CvbImagePlane
Image plane to work on.

style

Type: Stemmer.Cvb.FoundationCalibrationPatternStyle
Calibration pattern style visible in the image. (see CalibrationPatternStyle)

contrast

Type: Stemmer.Cvb.FoundationCalibrationPatternContrast
Selects whether the image shows BlackOnWhite or WhiteOnBlack dots.

gridSpacing

Type: SystemInt32

Spacing of the calibration dot grid in the target image.

Defines the distance of the points that will end up in the transformedPixels list.

minContrast

Type: SystemInt32

Minimum gray value contrast between the object and the background of the calibration target pattern.

Value to be set depends on the quality of the image taken from the pattern, but in a typical situation this contrast should not drop below 64 gray values, otherwise it might become difficult to extract the calibration points.

maxRatio

Type: SystemDouble

Maximum ratio between the biggest and the smallest calibration dot.

This value will be used to identify outliers when looking for calibration dots. It should be set high enough to allow for the area variations to be expected due to perspective distortions and small enough to eliminate the candidates that are either too big or too small to be valid calibration pattern dots.

Typically, values of about 3.0 to 5.0 are big enough - even if there is notable perspective distortion visible in the images. If an asymmetric calibration pattern has been selected, the ratio used for calculation will be adapted accordingly.

originalPixels

Type: Stemmer.CvbPoint2Dd
Point list to contain the locations of the calibration dots in the input image in pixel coordinates.

transformedPixels

Type: Stemmer.CvbPoint2Dd
Pixel list to contain the appropriate locations of the calibration dots in the target image of the calibration.

Note that a more convenient alternative is to call the method NonLinearTransformation.FromCalibrationPattern. It will do the list extraction and the generation of the transformation object in a single function call.

The image plane given to this method needs to contain a calibration pattern as generated by the method Create(CalibrationPatternStyle, CalibrationPatternContrast, Int32, Int32, Int32, Int32): A regularly spaced matrix of dots, the distance between the dots in x- and y-direction should be 2.5 times the diameter of the dots, if an asymmetric pattern was used, the bigger dots should have 2.5 times the area of the smaller dots (meaning that their radius is sqrt(2.5) times the radius of the small dots).

Note that, although the area of interest is given as a Area2D here (and in the processing of the Area2D the image's coordinate system will be respected), the actual output of this method uses PixelCoordinates! This seemingly inconsistent mix in this case is in fact useful, because a Area2D will better capture the actual location of a calibration pattern, especially if the image has been rotated, than a Rect style area of interest. But the calibration functions usually assume that the pixel lists are given in pixel coordinates.

To avoid misunderstandings and complications in the interpretation of the image content, it is recommended to use a default coordinate system on the input image.

Reference