estimateBoardCornersCamera

R2026b

Estimate corners of calibration board in camera frame

Since R2026a. Replaces estimateCheckerboardCorners3d.

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.

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

Estimate checkerboard corners in camera frame

Load an image containing a checkerboard pattern into the workspace.

I = imread(fullfile(toolboxdir("pointcloud"),"pcdata","calibration","images","01.png"));

Load the camera intrinsics from a previously saved mat file.

cameraIntrinsicFile = fullfile(toolboxdir("pointcloud"),"pcdata","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)

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)

Estimate AprilGrid Board Corners In Camera Frame

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)

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)

Input Arguments

imagePoints — Key point coordinates of calibration pattern in raw image

N-by-2 matrix | N-by-2-by-NumImages matrix

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.

intrinsics — Camera intrinsic parameters

cameraIntrinsics object

Camera intrinsic parameters, specified by a cameraIntrinsics (Computer Vision Toolbox) object.

patternDims — Pattern dimensions

2-element vector

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.

squareSize — Size of checkerboard square

positive scalar

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

checkerSize — Side length of ChArUco checker board square

positive scalar

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

tagSize — Size of AprilTag

positive scalar

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

tagSpacing — Space between two consecutive AprilTags

positive scalar

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

worldPoints — Generated world points

N-by-2 matrix

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].

originDistance — Distance from board edge to origin point

2-element vector

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

boardSize — Calibration board size

2-element vector

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

padding — Padding along each side of board

[0 0 0 0] (default) | 4-element row vector

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

Output Arguments

cornersCamera — Estimated 3-D board corners in camera frame

4-by-3-by-numImages matrix

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.

boardSize — Calibration board size

2-element vector

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.

  Checkerboard	ChArUco	AprilGrid

Version History

Introduced in R2026a

R2026a: Recommended over estimateCheckerboardCorners3d

Compared to estimateCheckerboardCorners3d, estimateBoardCornersCamera also supports ChArUco, AprilGrid and custom patterns, and a more modular approach that gives you the flexibility to select your own detection parameters when using detectCheckerboardPoints (Computer Vision Toolbox), detectCharucoBoardPoints (Computer Vision Toolbox) and detectAprilGridPoints (Computer Vision Toolbox).