img2world2d
Description
maps undistorted image points worldPoints
= img2world2d(imagePoints
,tform
,intrinsics
)imagePoints
, onto points on the
X-Y plane in world coordinates
worldPoints
, using the rigid transformation
tform
.
Examples
Map Image Points of Fisheye Image to World Coordinates
Map the points of a fisheye image to world coordinates and compare these points to the ground truth points. A series of checkerboard pattern images are used to estimate the fisheye parameters and calibrate the camera.
Load a set of checkerboard calibration images.
images = imageDatastore(fullfile(toolboxdir("vision"),"visiondata" ,... "calibration","gopro"));
Detect the checkerboard corners in the images. Leave the last image for testing.
[imagePoints,boardSize] = detectCheckerboardPoints(images.Files(1:end-1));
Generate the world coordinates of the checkerboard corners in the pattern-centric coordinate system, with the upper-left corner at (0,0).
squareSize = 29; % millimeters worldPoints = patternWorldPoints("checkerboard",boardSize,squareSize);
Estimate the fisheye camera parameters from the image and world points. Use the first image to get image size.
I = imread(images.Files{end}); imageSize = [size(I,1) size(I,2)]; fisheyeParams = estimateFisheyeParameters(imagePoints,worldPoints,imageSize); intrinsics = fisheyeParams.Intrinsics;
Find the reference object in the new image.
imagePoints = detectCheckerboardPoints(I,PartialDetections=false);
Calculate new extrinsics.
camExtrinsics = estimateExtrinsics(imagePoints,worldPoints,intrinsics);
Map image points to world coordinates in the X-Y plane.
newWorldPoints = img2world2d(imagePoints,camExtrinsics,intrinsics);
Compare estimated world points to the ground truth points.
plot(worldPoints(:,1),worldPoints(:,2),"gx"); hold on plot(newWorldPoints(:,1),newWorldPoints(:,2),"ro"); legend("Ground Truth","Estimates"); hold off
Input Arguments
imagePoints
— Image points
M-by-2 matrix
Image points, specified as an M-by-2 matrix containing M [x, y] coordinates of image points.
When you specify the cameraParams
argument as a cameraIntrinsics
object, img2world2d
does not account
for lens distortion. Therefore, the imagePoints
input must contain
image points detected in the undistorted image, or they must be undistorted using the
undistortPoints
function. For a fisheyeIntrinsics
object, the image points are distorted.
tform
— Transformation
rigidtform3d
object
Transformation of the camera in world coordinates, specified as a rigidtform3d
object.
intrinsics
— Camera intrinsics
cameraIntrinsics
object | fisheyeIntrinsics
object | cameraIntrinsicsKB
object
Camera intrinsics, specified as a cameraIntrinsics
, fisheyeIntrinsics
, or a cameraIntrinsicsKB
object. The object stores information about a camera’s
intrinsic calibration parameters, including the lens distortion parameters.
Output Arguments
worldPoints
— World coordinates
M-by-2 matrix
World coordinates, returned as an M-by-2 matrix. M represents the number of undistorted points in [x, y] world coordinates.
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.
Usage notes and limitations:
Code generation not supported for cameraIntrinsicsKB
object input.
Version History
Introduced in R2022bR2024a: Added support for the cameraIntrinsicsKB
object
Support added for the cameraIntrinsicsKB
object as the cameraParams
input.
R2022b: Recommended over pointsToWorld
Starting in R2022b, most Computer Vision Toolbox™ functions create and perform geometric transformations using the premultiply
convention. However, the pointsToWorld
function uses the postmultiply convention. Although there are no plans to remove
pointsToWorld
at this time, you can streamline your geometric
transformation workflows by switching to the img2world2d
function,
which supports the premultiply convention. For more information, see Migrate Geometric Transformations to Premultiply Convention.
See Also
Apps
Functions
world2img
|undistortImage
|undistortPoints
|estimateCameraParameters
|estimateExtrinsics
|triangulate
|triangulateMultiview
|reconstructScene
Objects
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