# cameraIntrinsicsToOpenCV

Convert camera intrinsic parameters from MATLAB to OpenCV

## Syntax

``[intrinsicMatrix,distortionCoefficients] = cameraIntrinsicsToOpenCV(intrinsics)``

## Description

example

````[intrinsicMatrix,distortionCoefficients] = cameraIntrinsicsToOpenCV(intrinsics)` converts a MATLAB® `cameraIntrinsics` or `cameraParameters` object, specified by `intrinsics`, to OpenCV camera intrinsic parameters.The OpenCV spatial coordinate system specifies the upper-left pixel center at (`0,0`), whereas the MATLAB spatial coordinate system specifies the pixel center at (`1,1`). The `cameraIntrinsicsToOpenCV` function compensates for this difference by subtracting 1 from both the x and y-values for the converted principal point.OpenCV camera intrinsic parameters do not include the skew of a pinhole camera model. Therefore, only the intrinsics that were estimated without the skew can be exported to OpenCV.```

## Examples

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Create a set of calibration images.

```images = imageDatastore(fullfile(toolboxdir('vision'),'visiondata', ... 'calibration','mono')); imageFileNames = images.Files;```

Detect the checkerboard calibration pattern in the images.

`[imagePoints,boardSize] = detectCheckerboardPoints(imageFileNames);`

Generate the world coordinates of the corners of the squares. Square size is in millimeters.

```squareSize = 29; worldPoints = generateCheckerboardPoints(boardSize,squareSize);```

Calibrate the camera.

```I = readimage(images,1); imageSize = [size(I,1),size(I,2)]; params = estimateCameraParameters(imagePoints,worldPoints, ... ImageSize=imageSize);```

Convert the intrinsic parameters to OpenCV format

`[intrinsicMatrix,distortionCoefficients] = cameraIntrinsicsToOpenCV(params);`

## Input Arguments

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Camera intrinsic parameters, specified as a `cameraIntrinsics` or a `cameraParameters` object.

## Output Arguments

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Camera intrinsics matrix formatted for OpenCV, returned as a 3-by-3 matrix of the form:

`$\left[\begin{array}{ccc}fx& 0& cx\\ 0& fy& cy\\ 0& 0& 1\end{array}\right]$`

where fx and fy are the focal lengths in the x and y-directions, and (cx,cy) is the principal point in OpenCV.

Camera radial and tangential distortion coefficients, returned as a five-element vector in the form [k1 k2 p1 p2 k3]. The values of k1, k2, and k3 describe the radial distortion and p1 and p2 describe the tangential distortion, specified in OpenCV.

## Version History

Introduced in R2021b