Calibration Reader

This example shows how to read calibration data stored on device over XLink. This example will print camera extrinsic and instrinsic parameters, along with other calibration values written on device (EEPROM).

Similar samples:

Camera intrinsics

Calibration also contains camera intrinsics and extrinsics parameters.

import depthai as dai

with dai.Device() as device:
  calibData = device.readCalibration()
  intrinsics = calibData.getCameraIntrinsics(dai.CameraBoardSocket.RIGHT)
  print('Right mono camera focal length in pixels:', intrinsics[0][0])

Here’s theoretical calculation of the focal length in pixels:

\[f_x = \text{width}_x \cdot \frac{1}{2 \cdot \tan \left(\frac{\text{HFOV}_x}{2}\frac{\pi}{180}\right)}\]

To get the HFOV you can use this script, which also works for wide-FOV cameras and allows you to specif alpha parameter.

With 400P (640x400) camera resolution where HFOV=71.9 degrees:

\[f_x = 640 \cdot \frac{1}{2 \cdot \tan \left(\frac{71.9}{2}\frac{\pi}{180}\right)} = 441.25\]

And for 800P (1280x800) camera resolution where HFOV=71.9 degrees:

\[f_x = 1280 \cdot \frac{1}{2 \cdot \tan \left(\frac{71.9}{2}\frac{\pi}{180}\right)} = 882.5\]

Setup

Please run the install script to download all required dependencies. Please note that this script must be ran from git context, so you have to download the depthai-python repository first and then run the script

git clone https://github.com/luxonis/depthai-python.git
cd depthai-python/examples
python3 install_requirements.py

For additional information, please follow installation guide

Source code

Python

C++

Also available on GitHub

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#!/usr/bin/env python3

import depthai as dai
import numpy as np
import sys
from pathlib import Path

# Connect Device
with dai.Device() as device:
    calibFile = str((Path(__file__).parent / Path(f"calib_{device.getMxId()}.json")).resolve().absolute())
    if len(sys.argv) > 1:
        calibFile = sys.argv[1]

    calibData = device.readCalibration()
    calibData.eepromToJsonFile(calibFile)

    M_rgb, width, height = calibData.getDefaultIntrinsics(dai.CameraBoardSocket.CAM_A)
    print("RGB Camera Default intrinsics...")
    print(M_rgb)
    print(width)
    print(height)

    if "OAK-1" in calibData.getEepromData().boardName or "BW1093OAK" in calibData.getEepromData().boardName:
        M_rgb = np.array(calibData.getCameraIntrinsics(dai.CameraBoardSocket.CAM_A, 1280, 720))
        print("RGB Camera resized intrinsics...")
        print(M_rgb)

        D_rgb = np.array(calibData.getDistortionCoefficients(dai.CameraBoardSocket.CAM_A))
        print("RGB Distortion Coefficients...")
        [print(name + ": " + value) for (name, value) in
         zip(["k1", "k2", "p1", "p2", "k3", "k4", "k5", "k6", "s1", "s2", "s3", "s4", "τx", "τy"],
             [str(data) for data in D_rgb])]

        print(f'RGB FOV {calibData.getFov(dai.CameraBoardSocket.CAM_A)}')

    else:
        M_rgb, width, height = calibData.getDefaultIntrinsics(dai.CameraBoardSocket.CAM_A)
        print("RGB Camera Default intrinsics...")
        print(M_rgb)
        print(width)
        print(height)

        M_rgb = np.array(calibData.getCameraIntrinsics(dai.CameraBoardSocket.CAM_A, 3840, 2160))
        print("RGB Camera resized intrinsics... 3840 x 2160 ")
        print(M_rgb)


        M_rgb = np.array(calibData.getCameraIntrinsics(dai.CameraBoardSocket.CAM_A, 4056, 3040 ))
        print("RGB Camera resized intrinsics... 4056 x 3040 ")
        print(M_rgb)


        M_left, width, height = calibData.getDefaultIntrinsics(dai.CameraBoardSocket.CAM_B)
        print("LEFT Camera Default intrinsics...")
        print(M_left)
        print(width)
        print(height)

        M_left = np.array(calibData.getCameraIntrinsics(dai.CameraBoardSocket.CAM_B, 1280, 720))
        print("LEFT Camera resized intrinsics...  1280 x 720")
        print(M_left)


        M_right = np.array(calibData.getCameraIntrinsics(dai.CameraBoardSocket.CAM_C, 1280, 720))
        print("RIGHT Camera resized intrinsics... 1280 x 720")
        print(M_right)

        D_left = np.array(calibData.getDistortionCoefficients(dai.CameraBoardSocket.CAM_B))
        print("LEFT Distortion Coefficients...")
        [print(name+": "+value) for (name, value) in zip(["k1","k2","p1","p2","k3","k4","k5","k6","s1","s2","s3","s4","τx","τy"],[str(data) for data in D_left])]

        D_right = np.array(calibData.getDistortionCoefficients(dai.CameraBoardSocket.CAM_C))
        print("RIGHT Distortion Coefficients...")
        [print(name+": "+value) for (name, value) in zip(["k1","k2","p1","p2","k3","k4","k5","k6","s1","s2","s3","s4","τx","τy"],[str(data) for data in D_right])]

        print(f"RGB FOV {calibData.getFov(dai.CameraBoardSocket.CAM_A)}, Mono FOV {calibData.getFov(dai.CameraBoardSocket.CAM_B)}")

        R1 = np.array(calibData.getStereoLeftRectificationRotation())
        R2 = np.array(calibData.getStereoRightRectificationRotation())
        M_right = np.array(calibData.getCameraIntrinsics(calibData.getStereoRightCameraId(), 1280, 720))

        H_left = np.matmul(np.matmul(M_right, R1), np.linalg.inv(M_left))
        print("LEFT Camera stereo rectification matrix...")
        print(H_left)

        H_right = np.matmul(np.matmul(M_right, R1), np.linalg.inv(M_right))
        print("RIGHT Camera stereo rectification matrix...")
        print(H_right)

        lr_extrinsics = np.array(calibData.getCameraExtrinsics(dai.CameraBoardSocket.CAM_B, dai.CameraBoardSocket.CAM_C))
        print("Transformation matrix of where left Camera is W.R.T right Camera's optical center")
        print(lr_extrinsics)

        l_rgb_extrinsics = np.array(calibData.getCameraExtrinsics(dai.CameraBoardSocket.CAM_B, dai.CameraBoardSocket.CAM_A))
        print("Transformation matrix of where left Camera is W.R.T RGB Camera's optical center")
        print(l_rgb_extrinsics)

Also available on GitHub

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#include <cstdio>
#include <iostream>
#include <string>

// Includes common necessary includes for development using depthai library
#include "depthai-shared/common/CameraBoardSocket.hpp"
#include "depthai-shared/common/EepromData.hpp"
#include "depthai/depthai.hpp"

void printMatrix(std::vector<std::vector<float>> matrix) {
    using namespace std;
    std::string out = "[";
    for(auto row : matrix) {
        out += "[";
        for(auto val : row) out += to_string(val) + ", ";
        out = out.substr(0, out.size() - 2) + "]\n";
    }
    out = out.substr(0, out.size() - 1) + "]\n\n";
    cout << out;
}

int main(int argc, char** argv) {
    using namespace std;

    // Connect Device
    dai::Device device;

    dai::CalibrationHandler calibData = device.readCalibration();
    // calibData.eepromToJsonFile(filename);
    std::vector<std::vector<float>> intrinsics;
    int width, height;

    cout << "Intrinsics from defaultIntrinsics function:" << endl;
    std::tie(intrinsics, width, height) = calibData.getDefaultIntrinsics(dai::CameraBoardSocket::CAM_C);
    printMatrix(intrinsics);

    cout << "Width: " << width << endl;
    cout << "Height: " << height << endl;

    cout << "Stereo baseline distance: " << calibData.getBaselineDistance() << " cm" << endl;

    cout << "Mono FOV from camera specs: " << calibData.getFov(dai::CameraBoardSocket::CAM_B)
         << ", calculated FOV: " << calibData.getFov(dai::CameraBoardSocket::CAM_B, false) << endl;

    cout << "Intrinsics from getCameraIntrinsics function full resolution:" << endl;
    intrinsics = calibData.getCameraIntrinsics(dai::CameraBoardSocket::CAM_C);
    printMatrix(intrinsics);

    cout << "Intrinsics from getCameraIntrinsics function 1280 x 720:" << endl;
    intrinsics = calibData.getCameraIntrinsics(dai::CameraBoardSocket::CAM_C, 1280, 720);
    printMatrix(intrinsics);

    cout << "Intrinsics from getCameraIntrinsics function 720 x 450:" << endl;
    intrinsics = calibData.getCameraIntrinsics(dai::CameraBoardSocket::CAM_C, 720);
    printMatrix(intrinsics);

    cout << "Intrinsics from getCameraIntrinsics function 600 x 1280:" << endl;
    intrinsics = calibData.getCameraIntrinsics(dai::CameraBoardSocket::CAM_C, 600, 1280);
    printMatrix(intrinsics);

    std::vector<std::vector<float>> extrinsics;

    cout << "Extrinsics from left->right test:" << endl;
    extrinsics = calibData.getCameraExtrinsics(dai::CameraBoardSocket::CAM_B, dai::CameraBoardSocket::CAM_C);
    printMatrix(extrinsics);

    cout << "Extrinsics from right->left test:" << endl;
    extrinsics = calibData.getCameraExtrinsics(dai::CameraBoardSocket::CAM_C, dai::CameraBoardSocket::CAM_B);
    printMatrix(extrinsics);

    cout << "Extrinsics from right->rgb test:" << endl;
    extrinsics = calibData.getCameraExtrinsics(dai::CameraBoardSocket::CAM_C, dai::CameraBoardSocket::CAM_A);
    printMatrix(extrinsics);

    cout << "Extrinsics from rgb->right test:" << endl;
    extrinsics = calibData.getCameraExtrinsics(dai::CameraBoardSocket::CAM_A, dai::CameraBoardSocket::CAM_C);
    printMatrix(extrinsics);

    cout << "Extrinsics from left->rgb test:" << endl;
    extrinsics = calibData.getCameraExtrinsics(dai::CameraBoardSocket::CAM_B, dai::CameraBoardSocket::CAM_A);
    printMatrix(extrinsics);

    return 0;
}

Got questions?

Head over to Discussion Forum for technical support or any other questions you might have.