getRotationMatrix2D

geometryfunctionOpenCV 5.0.0

import { getRotationMatrix2D } from '@banou/opencv-wasm'

Use after await initOpenCV(). See the initialization and named imports guide.

Explore visually: Affine transformations →

Map points with a linear transform plus translation, preserving straight lines and parallelism.

VISUAL WALKTHROUGHGeometry

REFERENCE INPUTSource coordinate frame

This example applies a known rotation, scale and translation to the source.

→

RESULTResampled output

The output preserves straight lines under this affine transform. Locations outside the source need an explicit border rule.

Illustrative example. The stages explain the method; they are not a live OpenCV execution.

Calculates an affine matrix of 2D rotation.

The function calculates the following matrix:

\begin{bmatrix} \alpha &  \beta & (1- \alpha )  \cdot \texttt{center.x} -  \beta \cdot \texttt{center.y} \\ - \beta &  \alpha &  \beta \cdot \texttt{center.x} + (1- \alpha )  \cdot \texttt{center.y} \end{bmatrix}

where

\begin{array}{l} \alpha =  \texttt{scale} \cdot \cos \texttt{angle} , \\ \beta =  \texttt{scale} \cdot \sin \texttt{angle} \end{array}

The transformation maps the rotation center to itself. If this is not the target, adjust the shift.

See: getAffineTransform, warpAffine, transform

getRotationMatrix2D(center: Point2f, angle: number, scale: number): Mat;

center

Center of the rotation in the source image.

angle

Rotation angle in degrees. Positive values mean counter-clockwise rotation (the coordinate origin is assumed to be the top-left corner).

scale

Isotropic scale factor.

Returns

The Mat result. Release returned native handles with using or delete(), including handles nested in results.

Upstream declaration ↗

These signatures describe this package. Upstream documentation can mention optional backends that are absent from this build. Check runtime compatibility before choosing a backend or file format.