Putting multiple video feed next to each other with OpenCV - opencv

Question

I have real-time video from 3 different cameras, I would like to resize and then put the videos next to each other and fit them on one screen, basically:
-------------------------------------
| CAM LEFT | CAM MIDDLE | CAM RIGHT |
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I have written the following code but for whatever reason I only have image on the LEFT side only. The middle and right side are replaced by a gray color background (I have no idea where that comes from). I have printed out all the coordinates and they look fine to me, with a total screen size of 1440 x 540 (I want the picture in the middle to be bigger).
- LEFT: 0,0,380,540
- MIDDLE: 380,0,680,540
- RIGHT: 1060,0,380,540
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/stitching.hpp"
#include <opencv2/opencv.hpp>
#include <opencv2/imgcodecs.hpp>
#include<iostream>
#include <fstream>
#include<conio.h> // may have to modify this line if not using Windows
int main(int argc, char **argv) {
int combinedScreenWidth = 1440;
int combinedScreenHeight = 540;
int rearCameraBiggerByThis = 100;
int combinedScreenWidthHalv = combinedScreenWidth / 3;
//initialize and allocate memory to load the video stream from camera
cv::VideoCapture cameraRight(0); // RIGHT CAM
cv::VideoCapture cameraMiddle(3); // REAR CAM
cv::VideoCapture cameraLeft(2); // LEFT CAM
if (!cameraRight.isOpened()) return 1;
if (!cameraMiddle.isOpened()) return 1;
if (!cameraLeft.isOpened()) return 1;
cv::Mat3b cameraRightFrame;
cv::Mat3b cameraMiddleFrame;
cv::Mat3b cameraLeftFrame;
cv::Mat3b cameraRightFrameMirrored;
cv::Mat3b cameraMiddleFrameMirrored;
cv::Mat3b cameraLeftFrameMirrored;
cv::Size camRightSize;
cv::Size camMiddleSize;
cv::Size camLeftSize;
cv::Mat3b cameraRightFrameMirroredResize;
cv::Mat3b cameraMiddleFrameMirroredResize;
cv::Mat3b cameraLeftFrameMirroredResize;
while (true) {
// Grab
cameraRight >> cameraRightFrame;
cameraMiddle >> cameraMiddleFrame;
cameraLeft >> cameraLeftFrame;
// Mirror
cv::flip(cameraRightFrame, cameraRightFrameMirrored, 1);
cv::flip(cameraMiddleFrame, cameraMiddleFrameMirrored, 1);
cv::flip(cameraLeftFrame, cameraLeftFrameMirrored, 1);
// Resize
camRightSize = cameraRightFrame.size();
camMiddleSize = cameraMiddleFrame.size();
camLeftSize = cameraLeftFrame.size();
std::cout << "----------------------> original camRightSize " << camRightSize.width << "x" << camRightSize.height << std::endl;
std::cout << "----------------------> original camMiddletSize " << camMiddleSize.width << "x" << camMiddleSize.height << std::endl;
std::cout << "----------------------> original camLeftSize " << camLeftSize.width << "x" << camLeftSize.height << std::endl;
resize(cameraRightFrameMirrored, cameraRightFrameMirroredResize, cv::Size(combinedScreenWidthHalv - rearCameraBiggerByThis, combinedScreenHeight));
resize(cameraMiddleFrameMirrored, cameraMiddleFrameMirroredResize, cv::Size(combinedScreenWidthHalv + 2 * rearCameraBiggerByThis, combinedScreenHeight));
resize(cameraLeftFrameMirrored, cameraLeftFrameMirroredResize, cv::Size(combinedScreenWidthHalv - rearCameraBiggerByThis, combinedScreenHeight));
camRightSize = cameraRightFrameMirroredResize.size();
camMiddleSize = cameraMiddleFrameMirroredResize.size();
camLeftSize = cameraLeftFrameMirroredResize.size();
std::cout << "----------------------> resized camRightSize " << camRightSize.width << "x" << camRightSize.height << std::endl;
std::cout << "----------------------> resized camMiddletSize " << camMiddleSize.width << "x" << camMiddleSize.height << std::endl;
std::cout << "----------------------> resized camLeftSize " << camLeftSize.width << "x" << camLeftSize.height << std::endl;
// Compilation
cv::Mat3b combinedFrame(camRightSize.height, camLeftSize.width + camMiddleSize.width + camRightSize.width);
// LEFT
std::cout << "LEFT: 0,0," << camLeftSize.width << "," << camLeftSize.height << std::endl;
cv::Mat3b leftSideOfScreen(combinedFrame, cv::Rect(0, 0, camLeftSize.width, camLeftSize.height));
cameraLeftFrameMirroredResize.copyTo(leftSideOfScreen);
// MIDDLE
std::cout << "MIDDLE: " << camLeftSize.width << ",0," << camMiddleSize.width << "," << camMiddleSize.height << std::endl;
cv::Mat3b middleSideOfScreen(combinedFrame, cv::Rect(camLeftSize.width, 0, camMiddleSize.width, camMiddleSize.height));
cameraRightFrameMirroredResize.copyTo(middleSideOfScreen);
// RIGHT
std::cout << "RIGHT: " << camLeftSize.width + camMiddleSize.width << ",0," << camRightSize.width << "," << camRightSize.height << std::endl;
cv::Mat3b rightSideOfScreen(combinedFrame, cv::Rect(camLeftSize.width + camMiddleSize.width, 0, camRightSize.width, camRightSize.height));
cameraMiddleFrameMirroredResize.copyTo(rightSideOfScreen);
// declare windows
cv::namedWindow("Combined", CV_WINDOW_NORMAL);
cv::setWindowProperty("Combined", CV_WND_PROP_FULLSCREEN, CV_WINDOW_FULLSCREEN);
cv::putText(combinedFrame, "LEFT", cv::Point(250, 50), cv::FONT_HERSHEY_PLAIN, 2.0, cv::Scalar(255, 255, 255), 2);
cv::putText(combinedFrame, "REAR", cv::Point(650, 50), cv::FONT_HERSHEY_PLAIN, 2.0, cv::Scalar(255, 255, 255), 2);
cv::putText(combinedFrame, "RIGHT", cv::Point(1050, 50), cv::FONT_HERSHEY_PLAIN, 2.0, cv::Scalar(255, 255, 255), 2);
cv::imshow("Combined", combinedFrame); // 1440 x 540 Screen size
//cv::imshow("Right Cam", cameraRightFrame);
//cv::imshow("Middle Cam", cameraMiddleFrame);
//cv::imshow("Left Cam", cameraLeftFrame);
//wait for 40 milliseconds
int c = cvWaitKey(1);
//exit the loop if user press "Esc" key (ASCII value of "Esc" is 27)
if (27 == char(c)) {
break;
}
}
return 0;
}