CamShift跟踪器：
RotatedRect CamShift(InputArray probImage, Rect& window, TermCriteria criteria)
- probImage – 对象直方图的反投影. 详细见函数 calcBackProject() .
- window – 初始搜索窗口
- criteria – meanShift 停止迭代搜索标准.
meanShift跟踪器：
int meanShift(InputArray probImage,
Rect& window, TermCriteria criteria)
- probImage – Back projection of the object histogram. See calcBackProject() for details.
- window – Initial search window.
- criteria – Stop criteria for the iterative search algorithm.
计算直方图的反投影：
void calcBackProject(const
Mat* arrays, int narrays, const int* channels, InputArray hist, OutputArray backProject, const float** ranges, double scale=1, bool uniform=true )
- arrays – 源数组。它们都应该有相同的深度，CV_8U或CV_32F，和相同的大小。
- narrays – 源数组数
- channels – 用于计算反投影的通道列表。通道的数量必须与直方图的维度相匹配。
- hist – 可以是密集或稀疏的输入直方图。
- backProject – 目标反投影是一个与数组array[0]相同大小和深度的单通道数组。.
- ranges – 查看函数 calcHist() .
- scale – 输出反投影的可选比例因子。
- uniform – 指示直方图是否是均匀的标志
直接看程序中的讲解吧：
#include <opencv2/video/tracking.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <iostream>
#include <ctype.h>
using namespace std;
using namespace cv;
Mat image;
bool backprojMode = false;//表示是否进入反向投影模式，true表示进入反向投影模式
bool selectObject = false;//选择要跟踪的初始目标，true代表正在用鼠标选择
int trackObject = 0;//代表目标跟踪数量
bool showHist = true;//是否显示直方图
Point origin; //保存鼠标选择第一次单机时点的位置
Rect selection; //用于保存选择的矩形框
int vmin = 10, vmax = 256, smin = 30;
void onMouse(int event, int x, int y, int, void*)
{
if (selectObject) //通过鼠标左键按下去选择矩形区域
{
selection.x = MIN(x, origin.x);//矩形顶点座标
selection.y = MIN(y, origin.y);
selection.width = std::abs(x - origin.x);//矩形宽
selection.height = std::abs(y - origin.y);//矩形高
selection &= Rect(0, 0, image.cols, image.rows);
}
switch (event)
{
case CV_EVENT_LBUTTONDOWN:
origin = Point(x, y); //刚点击时的点
selection = Rect(x, y, 0, 0);
selectObject = true; //正在用鼠标选择
break;
case CV_EVENT_LBUTTONUP:
selectObject = false; //鼠标停止选择
if (selection.width > 0 && selection.height > 0)
trackObject = -1;
break;
}
}
void help()
{
cout << "\nThis is a demo that shows mean-shift based tracking\n"
"You select a color objects such as your face and it tracks it.\n"
"This reads from video camera (0 by default, or the camera number the user enters\n"
"Usage: \n"
" ./camshiftdemo [camera number]\n";
cout << "\n\nHot keys: \n"
"\tESC - quit the program\n"
"\tc - stop the tracking\n"
"\tb - switch to/from backprojection view\n"
"\th - show/hide object histogram\n"
"\tp - pause video\n"
"To initialize tracking, select the object with mouse\n";
}
const char* keys =
{
"{1| | 0 | camera number}"
};
int main(int argc, const char** argv)
{
help();
VideoCapture cap; //定义一个摄像头捕捉的类对象
Rect trackWindow;
RotatedRect trackBox; //定义一个旋转的矩阵类对象
int hsize = 16;
float hranges[] = { 0, 180 };
const float* phranges = hranges;
CommandLineParser parser(argc, argv, keys); //命令解析器函数
int camNum = parser.get<int>("1");
cap.open(camNum);//直接调用成员函数打开摄像头
if (!cap.isOpened())
{
help();
cout << "***Could not initialize capturing...***\n";
cout << "Current parameter's value: \n";
parser.printParams();
return -1;
}
namedWindow("Histogram", 0);
namedWindow("CamShift Demo", 0);
setMouseCallback("CamShift Demo", onMouse, 0); //鼠标相应机制
createTrackbar("Vmin", "CamShift Demo", &vmin, 256, 0);
createTrackbar("Vmax", "CamShift Demo", &vmax, 256, 0);
createTrackbar("Smin", "CamShift Demo", &smin, 256, 0);
Mat frame, hsv, hue, mask, hist;
Mat histimg = Mat::zeros(200, 320, CV_8UC3), backproj;
bool paused = false;
for (;;)
{
if (!paused) //没有暂停
{
cap >> frame;//从摄像头抓取一帧图像并输出到frame中
if (frame.empty())
break;
}
frame.copyTo(image);
if (!paused)
{
cvtColor(image, hsv, CV_BGR2HSV);
if (trackObject)
{
int _vmin = vmin, _vmax = vmax;
//利用了hsv的3个通道
inRange(hsv, Scalar(0, smin, MIN(_vmin, _vmax)), Scalar(180, 256, MAX(_vmin, _vmax)), mask);
int ch[] = { 0, 0 };
//hue初始化为与hsv大小深度一样的矩阵，色调的度量是用角度表示的，红绿蓝之间相差120度，反色相差180度
hue.create(hsv.size(), hsv.depth());
mixChannels(&hsv, 1, &hue, 1, ch, 1);
if (trackObject < 0)//鼠标选择区域松开后，该函数内部又将其赋值1
{
//此处的构造函数roi用的时Mat hue的矩阵头，且roi的数据指针指向hue
Mat roi(hue, selection), maskroi(mask, selection);
calcHist(&roi, 1, 0, maskroi, hist, 1, &hsize, &phranges);
normalize(hist, hist, 0, 255, CV_MINMAX);
trackWindow = selection;
trackObject = 1;
histimg = Scalar::all(0);
int binW = histimg.cols / hsize;
Mat buf(1, hsize, CV_8UC3); //定义一个缓冲单bin矩阵
for (int i = 0; i < hsize; i++)
buf.at<Vec3b>(i) = Vec3b(saturate_cast<uchar>(i*180. / hsize), 255, 255);
cvtColor(buf, buf, CV_HSV2BGR);
for (int i = 0; i < hsize; i++)
{
int val = saturate_cast<int>(hist.at<float>(i)*histimg.rows / 255);
rectangle(histimg, Point(i*binW, histimg.rows), Point((i + 1)*binW, histimg.rows - val), Scalar(buf.at<Vec3b>(i)), -1, 8);
}
}
calcBackProject(&hue, 1, 0, hist, backproj, &phranges);
backproj &= mask;
trackBox = CamShift(backproj, trackWindow, TermCriteria(CV_TERMCRIT_EPS | CV_TERMCRIT_ITER, 10, 1));
//meanShift(backproj, trackWindow, TermCriteria(CV_TERMCRIT_EPS | CV_TERMCRIT_ITER, 10, 1));
if (trackWindow.area() <= 1)
{
int cols = backproj.cols, rows = backproj.rows;
int r = (MIN(cols, rows) + 5) / 6;
trackWindow = Rect(trackWindow.x - r, trackWindow.y - r, trackWindow.x + r, trackWindow.y + r) & Rect(0, 0, cols, rows);
}
if (backprojMode)
cvtColor(backproj, image, CV_GRAY2BGR);
ellipse(image, trackBox, Scalar(0, 0, 255), 3, CV_AA);
//rectangle(image, Point(trackWindow.x, trackWindow.y), Point(trackWindow.x + trackWindow.width, trackWindow.y + trackWindow.height), Scalar(0, 0, 255), -1, CV_AA);
}
}
//后面代码不管pause为真还是假都是要执行的
else if (trackObject < 0) //同时也是在按了暂停字母之后
paused = false;
if (selectObject && selection.width>0 && selection.height > 0)
{
Mat roi(image, selection);
bitwise_not(roi, roi);
}
imshow("CamShift Demo", image);
imshow("Histogram", histimg);
char c = (char)waitKey(10);
if (c == 27)
break;
switch (c)
{
case 'b':
backprojMode = !backprojMode;
case 'c':
trackObject = 0;
histimg = Scalar::all(0);
break;
case 'h':
showHist = !showHist;
if (!showHist)
destroyWindow("Histogram");
else
namedWindow("Histogram", 1);
break;
case 'p':
paused = !paused;
break;
default:
;
}
}
return 0;
}//meanShift(backproj, trackWindow, TermCriteria(CV_TERMCRIT_EPS | CV_TERMCRIT_ITER, 10, 1));
trackBox = CamShift(backproj, trackWindow, TermCriteria(CV_TERMCRIT_EPS | CV_TERMCRIT_ITER, 10, 1));
