opencv之简单的视频背景更新

主要用于摄像头固定，可以有效的更新背景，减少光照的因素的影响。

背景更新主要使用到了addweight这个函数
背景更新的公式
background = background + (frame - background) * alpha = background * (1 - alpha) + frame * alpha

alpha 更新速度

在opencv中也存在accumulateWeighted函数，与addweight函数实现功能一样，使用时候需要注意数据类型
src 输入图像 dst 输出图像

src.depth() == CV_8U   &&  dst.depth() == CV_32Fsrc.depth() == CV_8U   &&  dst.depth() == CV_64F src.depth() == CV_16U  &&  dst.depth() == CV_32Fsrc.depth() == CV_16U  &&  dst.depth() == CV_64Fsrc.depth() == CV_32F  &&  dst.depth() == CV_32Fsrc.depth() == CV_32F  &&  dst.depth() == CV_64Fsrc.depth() == CV_64F  &&  dst.depth() == CV_64F

Mat.converto（Mat，数据类型）；实现图像的数据类型转换。

convertScaleAbs(src,dst) 先缩放元素再取绝对值，最后转换格式为8bit型

#include<opencv2/imgproc/imgproc.hpp>#include<opencv2\core\core.hpp>#include<opencv2\highgui\highgui.hpp>#include<iostream>#include<string>using namespace cv;using namespace std;int main(){    string videofilename = "00011.AVI";    VideoCapture  video;    video.open(videofilename);    if (!video.isOpened())                     //判断视频是否读入    {        cout << "video open false" << endl;        return 1;    }    float alpha = 0.01;    int threhold = 25;    Mat frame;    Mat grayframe;    Mat grayMat;    Mat background;    Mat grayback;    Mat fromground;    Mat grayfrom;    while (video.read(frame))                                   //读入每一帧视频给frame    {        cvtColor(frame, grayframe, CV_RGB2GRAY);        grayframe.convertTo(grayMat,CV_32FC1);   //变图片的数据格式        if (grayback.empty())        {            grayframe.copyTo(background);            grayframe.convertTo(grayback, CV_32FC1);        }        absdiff(grayMat, grayback, grayfrom);                            //图片对应像素相减取绝对值        addWeighted(grayback, alpha, grayfrom, 1 - alpha, 0, grayback);        threshold(grayfrom, grayfrom, threhold, 255, CV_THRESH_BINARY);        convertScaleAbs(grayfrom, fromground);                   //        convertScaleAbs(grayback, background);        convertScaleAbs(grayMat, frame);        imshow("frame", frame);        imshow("background", background);        imshow("fromground", fromground);        waitKey(30);    }    return 0;}

frame图片

background图片

fromground图片

opencv当中还有高斯混合模型，后续