基于c++ opencv4.6做三帧间差法检测物体

三帧间差法是一种简单有效的运动目标检测方法，可以通过比较相邻的三帧图像像素值的差异来检测运动物体。下面是基于C++和OpenCV4.6实现三帧间差法的步骤：

1. 读取视频并初始化三个Mat对象：currentFrame, previousFrame和nextFrame。

VideoCapture capture("video.mp4");
Mat currentFrame, previousFrame, nextFrame;
capture >> previousFrame;
capture >> currentFrame;
capture >> nextFrame;

2. 将帧转换为灰度图像，以便进行差分计算。

cvtColor(previousFrame, previousFrame, COLOR_BGR2GRAY);
cvtColor(currentFrame, currentFrame, COLOR_BGR2GRAY);
cvtColor(nextFrame, nextFrame, COLOR_BGR2GRAY);

3. 计算相邻帧之间的差异，并将其存储在Mat对象中。

Mat diff1, diff2;
absdiff(previousFrame, currentFrame, diff1);
absdiff(currentFrame, nextFrame, diff2);

4. 对两个差分图像进行二值化处理，以便提取物体的运动。

threshold(diff1, diff1, 30, 255, THRESH_BINARY);
threshold(diff2, diff2, 30, 255, THRESH_BINARY);

5. 将两个二值化的图像进行逻辑与运算，以便提取出物体的移动区域。

Mat motionMask;
bitwise_and(diff1, diff2, motionMask);

6. 对运动区域进行形态学处理，以便去除噪声并填充空洞。

Mat kernel = getStructuringElement(MORPH_RECT, Size(3, 3));
morphologyEx(motionMask, motionMask, MORPH_OPEN, kernel);
morphologyEx(motionMask, motionMask, MORPH_CLOSE, kernel);

7. 显示运动区域，并等待按下任意键退出程序。

imshow("Motion Mask", motionMask);
waitKey(0);

完整的代码如下所示：

#include <opencv2/opencv.hpp>

using namespace cv;

int main()
{
    VideoCapture capture("video.mp4");
    Mat currentFrame, previousFrame, nextFrame;
    capture >> previousFrame;
    capture >> currentFrame;
    capture >> nextFrame;

    cvtColor(previousFrame, previousFrame, COLOR_BGR2GRAY);
    cvtColor(currentFrame, currentFrame, COLOR_BGR2GRAY);
    cvtColor(nextFrame, nextFrame, COLOR_BGR2GRAY);

    while (true)
    {
        Mat diff1, diff2;
        absdiff(previousFrame, currentFrame, diff1);
        absdiff(currentFrame, nextFrame, diff2);

        threshold(diff1, diff1, 30, 255, THRESH_BINARY);
        threshold(diff2, diff2, 30, 255, THRESH_BINARY);

        Mat motionMask;
        bitwise_and(diff1, diff2, motionMask);

        Mat kernel = getStructuringElement(MORPH_RECT, Size(3, 3));
        morphologyEx(motionMask, motionMask, MORPH_OPEN, kernel);
        morphologyEx(motionMask, motionMask, MORPH_CLOSE, kernel);

        imshow("Motion Mask", motionMask);

        char key = waitKey(1);
        if (key == 27) break;

        previousFrame = currentFrame;
        currentFrame = nextFrame;
        capture >> nextFrame;
        if (nextFrame.empty()) break;
        cvtColor(nextFrame, nextFrame, COLOR_BGR2GRAY);
    }

    return 0;
}