How to get the value of a specific pixel after conversion to hsv?

Question

I created a small program for detecting red color by converting the image to hsv. To detect red, I use the minimum range of 170 160 160 and the maximum range of 180 255 255. Thus, I got an hsv image that shows red in white. Now I want to know the value of this white pixel. I know the x, y coordinate. How to get pixel value? I am using python and cv2.

Answer 1

So you already have x and y,

-> Just create a ROI Mat with a size of 1X1

-> Convert HSV color space using CvtColor ()

- >

Mat src; //load image here
Mat HSV;
Mat RGB=image(Rect(x,y,1,1)); // use your x and y value

cvtColor(RGB, HSV,CV_BGR2HSV);
Vec3b hsv=HSV.at<Vec3b>(0,0);
int H=hsv.val[0]; //hue
int S=hsv.val[1]; //saturation
int V=hsv.val[2]; //value

++, RGB HSV , .

char window_name[30] = "HSV Segmentation";
Mat src;

static void onMouse( int event, int x, int y, int f, void* ){
 Mat image=src.clone();
 Vec3b rgb=image.at<Vec3b>(y,x);
 int B=rgb.val[0];
 int G=rgb.val[1];
 int R=rgb.val[2];

  Mat HSV;
  Mat RGB=image(Rect(x,y,1,1));
  cvtColor(RGB, HSV,CV_BGR2HSV);

    Vec3b hsv=HSV.at<Vec3b>(0,0);
    int H=hsv.val[0];
    int S=hsv.val[1];
    int V=hsv.val[2];

    char name[30];
    sprintf(name,"B=%d",B);
    putText(image,name, Point(150,40) , FONT_HERSHEY_SIMPLEX, .7, Scalar(0,255,0), 2,8,false );

    sprintf(name,"G=%d",G);
    putText(image,name, Point(150,80) , FONT_HERSHEY_SIMPLEX, .7, Scalar(0,255,0), 2,8,false );

    sprintf(name,"R=%d",R);
    putText(image,name, Point(150,120) , FONT_HERSHEY_SIMPLEX, .7, Scalar(0,255,0), 2,8,false );

    sprintf(name,"H=%d",H);
    putText(image,name, Point(25,40) , FONT_HERSHEY_SIMPLEX, .7, Scalar(0,255,0), 2,8,false );

    sprintf(name,"S=%d",S);
    putText(image,name, Point(25,80) , FONT_HERSHEY_SIMPLEX, .7, Scalar(0,255,0), 2,8,false );

    sprintf(name,"V=%d",V);
    putText(image,name, Point(25,120) , FONT_HERSHEY_SIMPLEX, .7, Scalar(0,255,0), 2,8,false );

    sprintf(name,"X=%d",x);
    putText(image,name, Point(25,300) , FONT_HERSHEY_SIMPLEX, .7, Scalar(0,0,255), 2,8,false );

    sprintf(name,"Y=%d",y);
    putText(image,name, Point(25,340) , FONT_HERSHEY_SIMPLEX, .7, Scalar(0,0,255), 2,8,false );

 //imwrite("hsv.jpg",image);
 imshow( window_name, image );
}



int main(){
 src = imread("bgr.png",1);
 imshow(window_name,src);
 setMouseCallback( window_name, onMouse, 0 );
 waitKey();  
 }