estimateBoardCornersCamera

Estimate corners of calibration board in camera frame

Since R2026a. Replaces estimateCheckerboardCorners3d.

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Syntax

cornersCamera = estimateBoardCornersCamera("checkerboard",imagePoints,intrinsics,patternDims,squareSize)
cornersCamera = estimateBoardCornersCamera("charuco-board",imagePoints,intrinsics,patternDims,checkerSize)
cornersCamera = estimateBoardCornersCamera("aprilgrid",imagePoints,intrinsics,patternDims,tagSize,tagSpacing)
[cornersCamera,boardSize] = estimateBoardCornersCamera(___)
[___] = estimateBoardCornersCamera(___,Padding=padding)
cornersCamera = estimateBoardCornersCamera(imagePoints,worldPoints,intrinsics,originDistance,boardSize)

Description

Estimate corners of a checkerboard, ChArUco board, AprilGrid, or a board with a custom calibration pattern in the camera frame.

Supported Calibration Patterns

cornersCamera = estimateBoardCornersCamera("checkerboard",imagePoints,intrinsics,patternDims,squareSize) estimates the 3-D corners of a checkerboard in the camera frame using 2-D image points, imagePoints, camera intrinsics, intrinsics, the pattern’s dimensions, patternDims, and the pattern's square size, squareSize.

example

cornersCamera = estimateBoardCornersCamera("charuco-board",imagePoints,intrinsics,patternDims,checkerSize) estimates the 3-D corners of a ChArUco board in the camera frame using the checker size, checkerSize.

cornersCamera = estimateBoardCornersCamera("aprilgrid",imagePoints,intrinsics,patternDims,tagSize,tagSpacing) estimates the 3-D corners of an AprilGrid board in the camera frame using the tag size, tagSize, and tag spacing.

[cornersCamera,boardSize] = estimateBoardCornersCamera(___) additionally returns the board size boardSize.

[___] = estimateBoardCornersCamera(___,Padding=padding) specifies the padding along each side of the board.

Custom Calibration Patterns

cornersCamera = estimateBoardCornersCamera(imagePoints,worldPoints,intrinsics,originDistance,boardSize) estimates the 3-D board corners using the image points imagePoints, world points worldPoints, camera intrinsics intrinsics, origin distance originDistance, and board size boardSize.

Examples

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Open Live Script

Load an image containing a checkerboard pattern into the workspace.

I = imread(fullfile(toolboxdir("lidar"),"lidardata","calibration","images","01.png"));

Load the camera intrinsics from a previously saved mat file.

cameraIntrinsicFile = fullfile(toolboxdir("lidar"),"lidardata","calibration","images","intrinsics.mat");
intrinsics = load(cameraIntrinsicFile).intrinsics;

Disable the warning for symmetric board usage. While symmetric boards are not recommended, the uniform padding in this case ensures symmetry does not affect the results.

currentState = warning;
warning("off","vision:calibrate:boardShouldBeAsymmetric")

Detect the checkerboard points.

[imagePoints,patternDims] = detectCheckerboardPoints(I,PartialDetections=false);

Restore the original warning state.

warning(currentState)

Visualize the detected checkerboard points.

figure
imshow(I)
hold on
plot(imagePoints(:,1),imagePoints(:,2),"ro",MarkerSize=3)

Figure contains an axes object. The hidden axes object contains 2 objects of type image, line. One or more of the lines displays its values using only markers

Specify the size of the checkerboard squares in millimeters.

squareSize = 100;

Specify the padding of the board in millimeters.

padding = [100 100 100 100];

Estimate the board corners in the camera frame.

cornersCamera = estimateBoardCornersCamera("checkerboard",imagePoints,...
    intrinsics,patternDims,squareSize,Padding=padding);

Undistort image for visualization.

J = undistortImage(I,intrinsics);

Project the corner points to the image.

cornersImage = projectLidarPointsOnImage(cornersCamera,intrinsics,rigidtform3d);

Visualize the estimated board corners in the undistorted image.

figure
imshow(J)
hold on
showShape("polygon",cornersImage,Color="red",LineWidth=2)

Figure contains an axes object. The hidden axes object contains an object of type image.

Open Live Script

Load an image containing an AprilGrid board into the workspace.

I = imread("AprilGridCalibrationBoardImage.jpg");

Load the camera intrinsics from a previously saved mat file.

intrinsics = load("intrinsics.mat").intrinsics;

Define the parameters for AprilGrid detection.

patternDims = [8 11];
markerFamily = "tag36h11";
minTagId = 300;

Detect AprilGrid points in the image.

imagePoints = detectAprilGridPoints(I,patternDims,markerFamily,MinTagID=minTagId);

Visualize the detected points in the image.

figure;
imshow(I)
hold on
plot(imagePoints(:,1),imagePoints(:,2),"ro",MarkerSize=2)

Figure contains an axes object. The hidden axes object contains 2 objects of type image, line. One or more of the lines displays its values using only markers

Define the parameters to estimate the board corners in the camera frame.

tagSize = 21.5;
tagSpacing = 6.5;
padding = [56 18 53 27];

Estimate board corners in the camera frame.

cornersCamera = estimateBoardCornersCamera("aprilgrid",imagePoints,intrinsics, ...
    patternDims,tagSize,tagSpacing,Padding=padding);

Undistort image for visualization.

J = undistortImage(I,intrinsics);

Project the corner points to the image.

cornersImage = projectLidarPointsOnImage(cornersCamera,intrinsics,rigidtform3d);

Visualize the estimated board corners in the undistorted image.

figure
imshow(J)
hold on
showShape("polygon",cornersImage,Color="red",LineWidth=3)

Figure contains an axes object. The hidden axes object contains an object of type image.

Input Arguments

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Key point coordinates of calibration pattern in raw image, specified by an N-by-2 matrix or an N-by-2-by-NumImages matrix. Partial detections are supported, but must include at least four non-collinear points.

Camera intrinsic parameters, specified by a cameraIntrinsics object.

Pattern dimensions, specified as a 2-element vector. The pattern board dimensions are defined as:

  • Checkerboard — Number of squares along the short side and along the long side.

  • ChArUco board — Number of checkers along the vertical and horizontal directions of the pattern, with the origin checker positioned at the top-left of the board and the minimum marker ID assigned to the checker immediately to the right of the origin.

  • AprilGrid board — Number of tags along the vertical and horizontal directions of the pattern, with the origin tag that corresponds to the minimum tag ID, located at the bottom-left corner

For more details, see the Tips section.

Size of checkerboard square, specified as a scalar in millimeters. For details, see the Tips section.

Side length of ChArUco checker board square, specified as a positive scalar in millimeters. For details, see the Tips section.

Size of AprilTag, specified as a positive scalar in millimeters. For details, see the Tips section.

Space between two consecutive AprilTags, specified as a positive scalar in millimeters. For details, see the Tips section.

Generated world points, specified as an N-by-2 matrix in world coordinates. The matrix contains N points with coordinates in the form [x y].

Distance from the board edge to the origin point in millimeters, specified as a 2-element vector of the form [xDistance yDistance].

Calibration board size in millimeters, specified as a 2-element vector of the form [sizeDim1 sizeDim2]. For details, see the Tips section.

Padding along each side of the board in millimeters, specified as a 4-element row vector. For details, see the Tips section.

Output Arguments

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Estimated board corners in the camera frame, returned as a 4-by-3-by-numImages matrix. For each set of keypoints that correspond to an image, the corresponding 4-by-3 matrix contains the location (x,y,z) coordinates of the four board corners based on the 2-D image keypoints. If board corner estimation fails for a set of points that correspond to an image, the corresponding matrix contains NaN values.

Calibration board size in millimeters, returned as a 2-element vector of the form [sizeDim1 sizeDim2].

Tips

  • Labeled diagrams of Checkerboard, ChArUco, and AprilGrid calibration patterns.

    CheckerboardChArUcoAprilGrid

Version History

Introduced in R2026a

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See Also

Apps

Functions

Topics