ILTransform Interface Reference

This interface represents 2D transformations of a coordinate system. More...

Inheritance diagram for ILTransform:

Public Member Functions
double	Build (ILPoints *srcPoints, ILPoints *dstPoints, LPVTransformType type)
ILTransform *	Rotate (double da, LPVAxis axis)
ILTransform *	Scale (double factorX, double factorY)
ILTransform *	Transform (ILTransform *tf)
ILTransform *	Translate (double offsetX, double offsetY)
Public Member Functions inherited from ILObject
ILObject *	Copy ()
LPVErrorCode	Load (LString filename)
void	Reset ()
LPVErrorCode	Save (LString filename)
BOOL	Valid ()

Properties
LMatrix33	Matrix [get, set]
	The @math_eq{3 \times 3} transformation matrix. By default, it's an identity matrix.

Detailed Description

This interface represents 2D transformations of a coordinate system.

A transformation specifies how to translate, scale, rotate or project the coordinate system, with the @math_eq{3 \times 3} matrix inside.

It can be built using the Scale(), Rotate() and Translate() functions, or modify the involved LMatrix33 directly. Alternatively, it can be built using Build() by computing the transformation between the corresponding point pairs.

To use this interface, you should create a LTransform object.

Example Code

C++

Code snippets: snippets/LinearTransform.cpp
ILTransformPtr tf = LTransform::Create();
double err = tf.Build(srcPoints, dstPoints, LPVTransformType::LPVTransformHomography);
if (err < 0 || err > 100) return; // failed, or the mapping error is too big
ILPointPtr newPoint = pnt->Transform(tf);
ILCirclePtr newCircle = circle->Transform(tf);

C#

Code snippets: snippets/LinearTransform.cs
LTransform tf = new LTransform();
double err = tf->Build(srcPoints, dstPoints, LPVTransformType.LPVTransformHomography);
if (err < 0 || err > 100) return; // failed, or the mapping error is too big
LPoint newPoint = pnt.Transform(tf);
LCircle newCircle = circle.Transform(tf);

COM

ILTransformPtr tf = LTransform::Create();
// or, ILTransformPtr tf(__uuidof(LTransform)), for absence of built-in Create functions (before 2.2.0)
double err = tf.Build(srcPoints, dstPoints, LPVTransformType::LPVTransformHomography);
if (err < 0 || err > 100) return; // failed, or the mapping error is too big
ILPointPtr newPoint = pnt->Transform(tf);
ILCirclePtr newCircle = circle->Transform(tf);

Member Function Documentation

Build()

double Build	(	ILPoints *	srcPoints,
		ILPoints *	dstPoints,
		LPVTransformType	type
	)

Build the transformation based on the given source and destination points, as:

\[ dst \sim H src \]

where the back-projection error is minimized.
It is recommended to provide at least 4 point pairs.

Parameters

[in]	srcPoints	The source points.
[in]	dstPoints	The destination points, same count as the source.
[in]	type	The transformation type. Usually it's set to LPVTransformHomography .

Return values

mapError

Return the mapping error of the result transformation which is the average of the distances between destination points and the mapping results. Return -1 for failure.

Rotate()

ILTransform* Rotate	(	double	da,
		LPVAxis	axis
	)

Rotate the coordinate system by the given angle about the specified axis and return a new transformation. Note that for rotation in the image coordinates, the rotation axis is LPVAxisZ (which is the default value) and the rotation angle is clockwise because the image's y-axis points downwards.

Parameters

[in]	da	The rotation angle in degrees.
[in]	axis	The rotation axis.

Return values

result

Return the new transformation.

Scale()

ILTransform* Scale	(	double	factorX,
		double	factorY
	)

Scale the coordinate system by the given factor and return a new transformation.

Parameters

[in]	factorX	The scale factor of x-coordinate
[in]	factorY	The scale factor of y-coordinate

Return values

result

Return the new transformation

Transform()

ILTransform* Transform

(

ILTransform *

tf

)

Transform the coordinate system by the given transformation and return a new transformation.

Parameters

[in]

tf

The transformation.

Return values

result

Return the new transformation.

Translate()

ILTransform* Translate	(	double	offsetX,
		double	offsetY
	)

Move the coordinate system by the given offset and return a new transformation.

Parameters

[in]	offsetX	The x-coordinate of the offset
[in]	offsetY	The y-coordinate of the offset

Return values

result

Return the new transformation