openCV学习笔记十八：摄像头中的色彩跟踪

在本节内容会涉及前面的鼠标操作同时涉及两个函数cvtColor（）、inRange（）等。
首先我们会利用鼠标操作在摄像头的图像中点击拉取一个范围，在这个范围中我们利用颜色空间转换，BGR图像转换为HSV，我们可以用它来提取一个彩色的物体。↔灰色,BGR↔HSV等等提取标志并跟踪。

// A code block
var foo = 'bar';

代码如下：

#include <iostream>
#include <cv.h>
#include <highgui.h>
#include <windows.h>

using namespace std;
using namespace cv;

Mat image;
bool backprojMode = false;
bool selectObject = false;
int trackObject = 0;
bool showHist = true;
Point origin;
Rect selection;
int vmin = 10, vmax = 256, smin = 30;

static void onMouse(int event, int x, int y, int, void*)
{
 if (selectObject)
 {
  selection.x = MIN(x, origin.x);
  selection.y = MIN(y, origin.y);
  selection.width = std::abs(x - origin.x);
  selection.height = std::abs(y - origin.y);
  selection &= Rect(0, 0, image.cols, image.rows);
  }
  switch (event)
 {
 case CV_EVENT_LBUTTONDOWN:
  origin = Point(x, y);
  selection = Rect(x, y, 0, 0);
  selectObject = true;
  break;
  case CV_EVENT_LBUTTONUP:
  selectObject = false;
  if (selection.width > 0 && selection.height > 0)
  trackObject = -1;
  break;
 }
 }
static 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;
 Rect trackWindow;
 int hsize = 16;
 float hranges[] = { 0, 180 };
 const float* phranges = hranges;
 CommandLineParser parser(argc, argv, keys);
 int camNum = parser.get<int>("1");
 cap.open(camNum);
f (!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);
 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, histimg = Mat::zeros(200, 320, CV_8UC3), backproj;
 bool paused = false;
for (;;)
 {
  if (!paused)
  {
   cap >> frame;
if (frame.empty())
    break;
  }
frame.copyTo(image);
if (!paused)
  {
   cvtColor(image, hsv, COLOR_BGR2HSV);
   if (trackObject)
   {
    int _vmin = vmin, _vmax = vmax;
    inRange(hsv, Scalar(0, smin, MIN(_vmin, _vmax)),
     Scalar(180, 256, MAX(_vmin, _vmax)), mask);
    int ch[] = { 0, 0 };
    hue.create(hsv.size(), hsv.depth());
    mixChannels(&hsv, 1, &hue, 1, ch, 1);
    if (trackObject < 0)
    {
     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);
     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;
    RotatedRect trackBox = CamShift(backproj, trackWindow,
    TermCriteria(CV_TERMCRIT_EPS | CV_TERMCRIT_ITER, 10, 1));
    if (trackWindow.area() <= 1)
    {
     int cols = backproj.cols, rows = backproj.rows, 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, COLOR_GRAY2BGR);
    ellipse(image, trackBox, Scalar(0, 0, 255), 3, CV_AA);
   }
  }
else if (trackObject < 0)
   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;
   break;
  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;
}

运行结果如下：