initInverseRectificationMap
import { initInverseRectificationMap } from '@banou/opencv-wasm'Use after await initOpenCV(). See the initialization and named imports guide.
Computes the projection and inverse-rectification transformation map. In essense, this is the inverse of #initUndistortRectifyMap to accomodate stereo-rectification of projectors ('inverse-cameras') in projector-camera pairs.
The function computes the joint projection and inverse rectification transformation and represents the result in the form of maps for #remap. The projected image looks like a distorted version of the original which, once projected by a projector, should visually match the original. In case of a monocular camera, newCameraMatrix is usually equal to cameraMatrix, or it can be computed by #getOptimalNewCameraMatrix for a better control over scaling. In case of a projector-camera pair, newCameraMatrix is normally set to P1 or P2 computed by #stereoRectify .
The projector is oriented differently in the coordinate space, according to R. In case of projector-camera pairs, this helps align the projector (in the same manner as #initUndistortRectifyMap for the camera) to create a stereo-rectified pair. This allows epipolar lines on both images to become horizontal and have the same y-coordinate (in case of a horizontally aligned projector-camera pair).
The function builds the maps for the inverse mapping algorithm that is used by #remap. That
is, for each pixel (u, v) in the destination (projected and inverse-rectified) image, the function
computes the corresponding coordinates in the source image (that is, in the original digital image). The following process is applied:
\begin{array}{l}
\text{newCameraMatrix}\\
x \leftarrow (u - {c'}_x)/{f'}_x \\
y \leftarrow (v - {c'}_y)/{f'}_y \\
\\\text{Undistortion}
\\\scriptsize{\textit{though equation shown is for radial undistortion, function implements cv::undistortPoints()}}\\
r^2 \leftarrow x^2 + y^2 \\
\theta \leftarrow \frac{1 + k_1 r^2 + k_2 r^4 + k_3 r^6}{1 + k_4 r^2 + k_5 r^4 + k_6 r^6}\\
x' \leftarrow \frac{x}{\theta} \\
y' \leftarrow \frac{y}{\theta} \\
\\\text{Rectification}\\
{[X\,Y\,W]} ^T \leftarrow R*[x' \, y' \, 1]^T \\
x'' \leftarrow X/W \\
y'' \leftarrow Y/W \\
\\\text{cameraMatrix}\\
map_x(u,v) \leftarrow x'' f_x + c_x \\
map_y(u,v) \leftarrow y'' f_y + c_y
\end{array}
where (k_1, k_2, p_1, p_2[, k_3[, k_4, k_5, k_6[, s_1, s_2, s_3, s_4[, \tau_x, \tau_y]]]])
are the distortion coefficients vector distCoeffs.
In case of a stereo-rectified projector-camera pair, this function is called for the projector while #initUndistortRectifyMap is called for the camera head. This is done after #stereoRectify, which in turn is called after #stereoCalibrate. If the projector-camera pair is not calibrated, it is still possible to compute the rectification transformations directly from the fundamental matrix using #stereoRectifyUncalibrated. For the projector and camera, the function computes homography H as the rectification transformation in a pixel domain, not a rotation matrix R in 3D space. R can be computed from H as
\texttt{R} = \texttt{cameraMatrix} ^{-1} \cdot \texttt{H} \cdot \texttt{cameraMatrix}
where cameraMatrix can be chosen arbitrarily.
initInverseRectificationMap(cameraMatrix: Mat, distCoeffs: Mat, R: Mat, newCameraMatrix: Mat, size: Size, m1type: number, map1: Mat, map2: Mat): void;cameraMatrixInput camera matrix
A=\vecthreethree{f_x}{0}{c_x}{0}{f_y}{c_y}{0}{0}{1}.distCoeffsInput vector of distortion coefficients
(k_1, k_2, p_1, p_2[, k_3[, k_4, k_5, k_6[, s_1, s_2, s_3, s_4[, \tau_x, \tau_y]]]])of 4, 5, 8, 12 or 14 elements. If the vector is NULL/empty, the zero distortion coefficients are assumed.ROptional rectification transformation in the object space (3x3 matrix). R1 or R2, computed by #stereoRectify can be passed here. If the matrix is empty, the identity transformation is assumed.
newCameraMatrixNew camera matrix
A'=\vecthreethree{f_x'}{0}{c_x'}{0}{f_y'}{c_y'}{0}{0}{1}.sizeDistorted image size.
m1typeType of the first output map. Can be CV_32FC1, CV_32FC2 or CV_16SC2, see #convertMaps
map1Output destination, filled by the native operation. The first output map for #remap.
map2Output destination, filled by the native operation. The second output map for #remap.
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.