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CreateRectificationMap_Advanced

Header:	FIL.h
Namespace:	fil
Module:	Calibration

Computes a spatial map for transforming distorted images to rectified images defined in world coordinate plane. Allows for flexible definition of output geometry.

Applications: Rarely seen special edge cases. Usually it is sufficient to use CreateRectificationMap_PixelUnits or CreateRectificationMap_WorldUnits filters.

Syntax

void fil::CreateRectificationMap_Advanced
(
	const fil::ImageFormat& inImageFormat,
	const fil::CreateSpatialMapUnit::Type& inCenterPointType,
	const ftl::Optional<fil::Point2D>& inCenterPoint,
	const fil::CreateSpatialMapUnit::Type& inOutputSizeType,
	const ftl::Optional<float>& inOutputWidth,
	const ftl::Optional<float>& inOutputHeight,
	const ftl::Optional<float>& inWorldScale,
	bool inInvertedWorldY,
	fil::InterpolationMethod::Type inInterpolationMethod,
	const fil::RectificationTransform& inTransform,
	fil::RectificationMap& outRectificationMap
)

Parameters

Name	Type	Range	Default	Description
inImageFormat	const ImageFormat&			Input image format.
inCenterPointType	const CreateSpatialMapUnit::Type&		Pixels	Specifies units of measurement of inCenterPoint.
inCenterPoint	const Optional<Point2D>&		NIL	Specifies a point which will be the center of output image. Depending on inCenterPointType it can be either defined in pixels of input image or in world units. Defaults to the center of input image.
inOutputSizeType	const CreateSpatialMapUnit::Type&		Pixels	Specifies units of measurement of inOutputWidth and inOutputHeight.
inOutputWidth	const Optional<float>&	0.001 -	NIL	Specifies the size of output image. Depending on inOutputSizeType it can be either defined in pixels or world units. Defaults to the size of input image.
inOutputHeight	const Optional<float>&	0.001 -	NIL	Specifies the size of output image. Depending on inOutputSizeType it can be either defined in pixels or world units. Defaults to the size of input image.
inWorldScale	const Optional<float>&	0.001 -	NIL	[pix / world unit] Specifies the scale for output image. By default scale is calculated such that there will be no rescaling at the inCenterPoint.
inInvertedWorldY	bool		False	Set to true if world coordinate system has right-handed orientation, also known as mathematical or standard. This effectively mirrors the rectified image vertically.
inInterpolationMethod	InterpolationMethod::Type		Bilinear
inTransform	const RectificationTransform&			Transform's camera model is needed for undistortion of image, when not supplied the generated map will assume undistorted image on input. Transform's homography is needed for transforming to given world plane, when not supplied the generated map will only remove distortion of image.
outRectificationMap	RectificationMap&

Description

Creates a RectificationMap, which is used by RectifyImage filter for image rectification onto a defined world plane. Point locations on rectified images are related to the world plane (defined by inTransform) only by translation and scaling.

This filter allows for the most flexible definition of output canvas geometry, however for most cases filters CreateRectificationMap_PixelUnits or CreateRectificationMap_WorldUnits suffice.

The filter may be used to generate a map which only removes a lens distortion in the image – to achieve this behaviour attach a camera model directly to inTransform (i.e. do not provide a homography matrix).

The inTransform may not contain a camera model – in such case the the generated map will assume undistorted image on input.

The output image dimensions, resolution and cropping are specified by:

inCenterPoint - the point which will be the center of output image. Can be selected on the input image or it can be defined in world units - see inCenterPointType
inOutputWidth,inOutputHeight - the size of output image, can be defined in output pixels or in world units - see inOutputSizeType
inWorldScale - the scale for output image, defined in pixels per world unit.

For example, if one is interested in area spanning from (0,0) to (10,6) world coordinate, with resolution 100 pixels / world unit, then inputs would be set as follows:

inCenterPoint = (5,3)
inCenterPointType = WorldUnits
inOutputWidth = 10
inOutputHeight = 6
inOutputSizeType = WorldUnits
inWorldScale = 100

Auxiliary data contained inside the RectificationMap describes the relation of rectified image to the world plane.

Examples


Left: original image, as captured by a camera, with mild lens distortion present. Right: rectified image with annotated length measurement.