Color-based object detection using Hue and Saturation thresholding

函数原型：C++: int createTrackbar(const
string& trackbarname, const string& winname,
int* value, int count,
TrackbarCallback onChange=0, void* userdata=0)

//Color_based object detection using Hue and Saturation thresholding

/*1、Program to display a video from attached default camera device 

  and detect colored blobs using H and S thresholding.

  2、Remove noise using opening and closing morphological operations*/

#include <opencv2/opencv.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <iostream>
using namespace std;
using namespace cv;

int hs_slider=0,low_slider=30,high_slider=100;
int low_h=30,low_s=30,high_h=100,high_s=100;
void on_hs_trackbar(int ,void *)
{
switch (hs_slider)
{
case 0:
setTrackbarPos("Low threshold","Segmentation",low_h);
setTrackbarPos("High threshold","Segmentation",high_h);
break;
case 1:
setTrackbarPos("Low threshold","Segmentation",low_s);
setTrackbarPos("High threshold","Segmentation",high_s);
break;
}

}
void on_low_thresh_trackbar(int ,void *)
{
switch(hs_slider)
{
case 0:
low_h=min(high_slider-1,low_slider);
setTrackbarPos("Low threshold","Segmentation",low_h);
break;
case 1:
low_s=min(high_slider-1,low_slider);
setTrackbarPos("Low threshold","Segmentation",low_s);
break;
}
}
void on_high_thresh_trackbar(int ,void *)
{
switch(hs_slider)
{
case 0:
high_h=max(low_slider+1,high_slider);
setTrackbarPos("High threshold","Segmentation",high_h);
break;
case 1:
high_s=max(low_slider+1,high_slider);
setTrackbarPos("High threshold","Segmentation",high_s);
break;
}
}
int main()
{
VideoCapture cap(0);
if(!cap.isOpened())//check if the file was open properly
{
cout<<" failed to open Capture"<<endl;
return -1;
}
namedWindow("Video");
namedWindow("Segmentation");
//creat trackbar
createTrackbar("0.H\n1.S","Segmentation",&hs_slider,1,on_hs_trackbar);
createTrackbar("Low threshold","Segmentation",&low_slider,255,on_low_thresh_trackbar);
createTrackbar("High threshold","Segmentation",&high_slider,255,on_high_thresh_trackbar);
//
while (char(waitKey(1))!='q'&&cap.isOpened())
{
Mat frame,frame_thresholded,frame_hsv;
cap>>frame;
cvtColor(frame,frame_hsv,CV_BGR2HSV);
//Check if the video is over
if (frame.empty())
{
cout<<"Video over"<<endl;
break;
}
//extract the Hue and Saturation channels
int from_to[]={0,0,1,1};
Mat hs(frame_hsv.size(),CV_8UC2);
mixChannels(&frame_hsv,1,&hs,1,from_to,2);
//check the image for a specific range of H and S
inRange(hs,Scalar(low_h,low_s),Scalar(high_h,high_s),frame_thresholded);
//open and close to remove noise
Mat str_el=getStructuringElement(MORPH_ELLIPSE,Size(7,7));
morphologyEx(frame_thresholded,frame_thresholded,MORPH_OPEN,str_el);
morphologyEx(frame_thresholded,frame_thresholded,MORPH_CLOSE,str_el);
imshow("Video",frame);
imshow("Segmentation",frame_thresholded);
}
return 0;
}