Note: This tutorial is a record of teacher Jia Zhigang ’s opencv course study. I would like to express my gratitude to teacher Jia.
The color-based object tracking and filtering steps are as follows:
1. inRange filtering
2. Morphological operation extraction
3. Contour search
4 . Obtain the circumscribed rectangle
5. Position calibration
#include <opencv2/opencv.hpp>
#include <iostream>
using namespace std;
using namespace cv;
Rect roi;
void processFrame(Mat &binary, Rect &rect);
int main(int argc, char** argv) {
// load video
VideoCapture capture;
capture.open("/home/fuhong/code/cpp/opencv_learning/src/object_tracing/video/video_006.mp4");
if (!capture.isOpened()) {
printf("could not find video file");
return -1;
}
Mat frame, mask;
Mat kernel1 = getStructuringElement(MORPH_RECT, Size(3, 3), Point(-1, -1));
Mat kernel2 = getStructuringElement(MORPH_RECT, Size(5, 5), Point(-1, -1));
namedWindow("input video", CV_WINDOW_AUTOSIZE);
namedWindow("track mask", CV_WINDOW_AUTOSIZE);
while (capture.read(frame)) {
//inrange()函数:提取两个像素值范围内的像素点
inRange(frame, Scalar(0, 127, 0), Scalar(120, 255, 120), mask);
morphologyEx(mask, mask, MORPH_OPEN, kernel1, Point(-1, -1), 1); //开操作，可以去掉小的对象，假设对象是前景色，背景是黑色
dilate(mask, mask, kernel2, Point(-1, -1), 4); //膨胀操作
imshow("track mask", mask);
processFrame(mask, roi);
rectangle(frame, roi, Scalar(0, 0, 255), 3, 8, 0);
imshow("input video", frame);
// trigger exit
char c = waitKey(100);
if (c == 27) {
break;
}
}
capture.release(); //释放资源
waitKey(0);
return 0;
}
/*!
* @note .作用: 从所有的轮廓中找出面积最大的轮廓所在的boundingRect包围矩形。
* @param binary : 二值化图像
* @param rect ： 感兴趣区域
*/
void processFrame(Mat &binary, Rect &rect) {
vector<vector<Point>> contours;
vector<Vec4i> hireachy;
findContours(binary, contours, hireachy, RETR_EXTERNAL, CHAIN_APPROX_SIMPLE, Point(0, 0));
if (contours.size() > 0) {
double maxArea = 0.0;
for (size_t t = 0; t < contours.size(); t++) {
double area = contourArea(contours[static_cast<int>(t)]);
if (area > maxArea) {
maxArea = area;
rect = boundingRect(contours[static_cast<int>(t)]);
}
}
}
else {
rect.x = rect.y = rect.width = rect.height = 0;
}
}
The effect is as follows:
