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asked Jul 13 '12

imran gravatar image

Using Hue and Saturation to calculate Backprojection of an object in OpenCV

In OpenCV it is possible to calculate the backprojection of a selected area using only the Hue component in the HSV image (CamSHIFT example). I am trying to do the same thing but using both the Hue and Saturation components to compute the backprojection. I am not sure whether I am doing it correctly. Below is my code,

The functions that I am not to sure about are

  • int ch[] = { 0,0, 1,0}; // here from what I understand, for the variable fromTo needed in the mixChannels function, does this hsv[0]->hue[0], hsv[0]->saturation[1]
  • mixChannels(&hsv, 1, out, 2, ch, 2); // from what I understand should split, hue and saturation from hsv
  • calcHist(planes[1], 1, 0, maskroi, hist, 1, hdims, ranges);

If someone has done something similar, could you please advise.

\\code

Mat backProjectObject(Mat frame, Point pnt){

   int hsize = 16, ssize = 16;
   int hdims[] = { hsize, ssize };
   float h_ranges[] = { 0,180 };
   float s_ranges[] = { 0,255 };
   const float* ranges[] = { h_ranges, s_ranges };

Mat hsv, hue, saturation, mask, histimg = Mat::zeros(200, 320, CV_8UC3);
   MatND hist, backproj;

   Rect selection;
   int vmin = 10, vmax = 256, smin = 30;

   cvtColor(frame, hsv, CV_BGR2HSV);

   selection.x = pnt.x; //selected center for the area
   selection.y = pnt.y; //selected center for the area
   selection.width = 20; //selected center for the area
   selection.height = 20; //selected center for the area

   selection &= Rect(0, 0, frame.cols, frame.rows);

   int _vmin = vmin, _vmax = vmax;

   inRange(hsv, Scalar(0, smin, MIN(_vmin,_vmax)), Scalar(180, 256, MAX(_vmin, _vmax)), mask);
   hue.create(hsv.size(), hsv.depth());
   saturation.create(hsv.size(), hsv.depth());
   Mat out[] = { hue, saturation };
   int ch[] = { 0,0, 1,0};
Mat planes[2][2];

   mixChannels(&hsv, 1, out, 2, ch, 2);

   planes[0][0] = hue; 
   planes[0][1] = saturation;

Mat roi1(hue, selection), roi2(saturation, selection), maskroi(mask, selection);

planes[1][0] = roi1; //selected template
   planes[1][1] = roi2; //selected template        

  calcHist(planes[1], 1, 0, maskroi, hist, 1, hdims, ranges);
   normalize(hist, hist, 0, 255, CV_MINMAX);

  calcBackProject(planes[0], 1, 0, hist, backproj, ranges);
backproj &= mask;
   threshold( backproj, backproj, 250, 255,0 );

   return backproj;

}

click to hide/show revision 2
No.2 Revision

updated Jul 13 '12

Using Hue and Saturation to calculate Backprojection of an object in OpenCV

In OpenCV it is possible to calculate the backprojection of a selected area using only the Hue component in the HSV image (CamSHIFT example). I am trying to do the same thing but using both the Hue and Saturation components to compute the backprojection. I am not sure whether I am doing it correctly. Below is my code,

The functions that I am not to sure about are

  • int ch[] = { 0,0, 1,0}; // here from what I understand, for the variable fromTo needed in the mixChannels function, does this hsv[0]->hue[0], hsv[0]->saturation[1]
  • mixChannels(&hsv, 1, out, 2, ch, 2); // from what I understand should split, hue and saturation from hsv
  • calcHist(planes[1], 1, 0, maskroi, hist, 1, hdims, ranges);

If someone has done something similar, could you please advise.

\\code

Mat backProjectObject(Mat frame, Point pnt){

   int hsize = 16, ssize = 16;
   int hdims[] = { hsize, ssize };
   float h_ranges[] = { 0,180 };
   float s_ranges[] = { 0,255 };
   const float* ranges[] = { h_ranges, s_ranges };

 Mat hsv, hue, saturation, mask, histimg = Mat::zeros(200, 320, CV_8UC3);
   MatND hist, backproj;

   Rect selection;
   int vmin = 10, vmax = 256, smin = 30;

   cvtColor(frame, hsv, CV_BGR2HSV);

   selection.x = pnt.x; //selected center for the area
   selection.y = pnt.y; //selected center for the area
   selection.width = 20; //selected center for the area
   selection.height = 20; //selected center for the area

   selection &= Rect(0, 0, frame.cols, frame.rows);

   int _vmin = vmin, _vmax = vmax;

   inRange(hsv, Scalar(0, smin, MIN(_vmin,_vmax)), Scalar(180, 256, MAX(_vmin, _vmax)), mask);
   hue.create(hsv.size(), hsv.depth());
   saturation.create(hsv.size(), hsv.depth());
   Mat out[] = { hue, saturation };
   int ch[] = { 0,0, 1,0};
 Mat planes[2][2];

   mixChannels(&hsv, 1, out, 2, ch, 2);

   planes[0][0] = hue; 
   planes[0][1] = saturation;

 Mat roi1(hue, selection), roi2(saturation, selection), maskroi(mask, selection);

planes[1][0] = roi1; //selected template
   planes[1][1] = roi2; //selected template        

  calcHist(planes[1], 1, 0, maskroi, hist, 1, hdims, ranges);
   normalize(hist, hist, 0, 255, CV_MINMAX);

  calcBackProject(planes[0], 1, 0, hist, backproj, ranges);
backproj &= mask;
   threshold( backproj, backproj, 250, 255,0 );

   return backproj;

}

click to hide/show revision 3
No.3 Revision

updated Jul 13 '12

Using Hue and Saturation to calculate Backprojection of an object in OpenCV

In OpenCV it is possible to calculate the backprojection of a selected area using only the Hue component in the HSV image (CamSHIFT example). I am trying to do the same thing but using both the Hue and Saturation components to compute the backprojection. I am not sure whether I am doing it correctly. Below is my code,

The functions that I am not to sure about are

  • int ch[] = { 0,0, 1,0}; // here from what I understand, for the variable fromTo needed in the mixChannels function, does this hsv[0]->hue[0], hsv[0]->saturation[1]
  • mixChannels(&hsv, 1, out, 2, ch, 2); // from what I understand should split, hue and saturation from hsv
  • calcHist(planes[1], 1, 0, maskroi, hist, 1, hdims, ranges);

If someone has done something similar, could you please advise.

\\code

Mat backProjectObject(Mat frame, Point pnt){

   int hsize = 16, ssize = 16;
   int hdims[] = { hsize, ssize };
   float h_ranges[] = { 0,180 };
   float s_ranges[] = { 0,255 };
   const float* ranges[] = { h_ranges, s_ranges };

   Mat hsv, hue, saturation, mask, histimg = Mat::zeros(200, 320, CV_8UC3);
   MatND hist, backproj;

   Rect selection;
   int vmin = 10, vmax = 256, smin = 30;

   cvtColor(frame, hsv, CV_BGR2HSV);

   selection.x = pnt.x; //selected center for the area
   selection.y = pnt.y; //selected center for the area
   selection.width = 20; //selected center for the area
   selection.height = 20; //selected center for the area

   selection &= Rect(0, 0, frame.cols, frame.rows);

   int _vmin = vmin, _vmax = vmax;

   inRange(hsv, Scalar(0, smin, MIN(_vmin,_vmax)), Scalar(180, 256, MAX(_vmin, _vmax)), mask);
   hue.create(hsv.size(), hsv.depth());
   saturation.create(hsv.size(), hsv.depth());
   Mat out[] = { hue, saturation };
   int ch[] = { 0,0, 1,0};
   Mat planes[2][2];

   mixChannels(&hsv, 1, out, 2, ch, 2);

   planes[0][0] = hue; 
   planes[0][1] = saturation;

   Mat roi1(hue, selection), roi2(saturation, selection), maskroi(mask, selection);

 planes[1][0] = roi1; //selected template
   planes[1][1] = roi2; //selected template        

   calcHist(planes[1], 1, 0, maskroi, hist, 1, hdims, ranges);
   normalize(hist, hist, 0, 255, CV_MINMAX);

   calcBackProject(planes[0], 1, 0, hist, backproj, ranges);
backproj &= mask;
   threshold( backproj, backproj, 250, 255,0 );

   return backproj;

}

click to hide/show revision 4
No.4 Revision

updated Jul 13 '12

Using Hue and Saturation to calculate Backprojection of an object in OpenCV

In OpenCV it is possible to calculate the backprojection of a selected area using only the Hue component in the HSV image (CamSHIFT example). I am trying to do the same thing but using both the Hue and Saturation components to compute the backprojection. I am not sure whether I am doing it correctly. Below is my code,

The functions that I am not to sure about are

  • int ch[] = { 0,0, 1,0}; // here from what I understand, for the variable fromTo needed in the mixChannels function, does this hsv[0]->hue[0], hsv[0]->saturation[1]
  • mixChannels(&hsv, 1, out, 2, ch, 2); // from what I understand should split, hue and saturation from hsv
  • calcHist(planes[1], 1, 0, maskroi, hist, 1, hdims, ranges);

If someone has done something similar, could you please advise.

\\code

Mat backProjectObject(Mat frame, Point pnt){

   int hsize = 16, ssize = 16;
   int hdims[] = { hsize, ssize };
   float h_ranges[] = { 0,180 };
   float s_ranges[] = { 0,255 };
   const float* ranges[] = { h_ranges, s_ranges };

   Mat hsv, hue, saturation, mask, histimg = Mat::zeros(200, 320, CV_8UC3);
   MatND hist, backproj;

   Rect selection;
   int vmin = 10, vmax = 256, smin = 30;

   cvtColor(frame, hsv, CV_BGR2HSV);

   selection.x = pnt.x; //selected center for the area
   selection.y = pnt.y; //selected center for the area
   selection.width = 20; //selected center for the area
   selection.height = 20; //selected center for the area

   selection &= Rect(0, 0, frame.cols, frame.rows);

   int _vmin = vmin, _vmax = vmax;

   inRange(hsv, Scalar(0, smin, MIN(_vmin,_vmax)), Scalar(180, 256, MAX(_vmin, _vmax)), mask);
   hue.create(hsv.size(), hsv.depth());
   saturation.create(hsv.size(), hsv.depth());
   Mat out[] = { hue, saturation };
   int ch[] = { 0,0, 1,0};
   Mat planes[2][2];

   mixChannels(&hsv, 1, out, 2, ch, 2);

   planes[0][0] = hue; 
   planes[0][1] = saturation;

   Mat roi1(hue, selection), roi2(saturation, selection), maskroi(mask, selection);

   planes[1][0] = roi1; //selected template
   planes[1][1] = roi2; //selected template        

   calcHist(planes[1], 1, 0, maskroi, hist, 1, hdims, ranges);
   normalize(hist, hist, 0, 255, CV_MINMAX);

   calcBackProject(planes[0], 1, 0, hist, backproj, ranges);
 backproj &= mask;
   threshold( backproj, backproj, 250, 255,0 );

   return backproj;

}

click to hide/show revision 5
No.5 Revision

updated Jul 16 '12

Kirill Kornyakov gravatar image

Using Hue and Saturation to calculate Backprojection of an object in OpenCVobject

In OpenCV it is possible to calculate the backprojection of a selected area using only the Hue component in the HSV image (CamSHIFT example). I am trying to do the same thing but using both the Hue and Saturation components to compute the backprojection. I am not sure whether I am doing it correctly. Below is my code,

The functions that I am not to sure about are

  • int ch[] = { 0,0, 1,0}; // here from what I understand, for the variable fromTo needed in the mixChannels function, does this hsv[0]->hue[0], hsv[0]->saturation[1]
  • mixChannels(&hsv, 1, out, 2, ch, 2); // from what I understand should split, hue and saturation from hsv
  • calcHist(planes[1], 1, 0, maskroi, hist, 1, hdims, ranges);

If someone has done something similar, could you please advise.

\\code

Mat backProjectObject(Mat frame, Point pnt){

   int hsize = 16, ssize = 16;
   int hdims[] = { hsize, ssize };
   float h_ranges[] = { 0,180 };
   float s_ranges[] = { 0,255 };
   const float* ranges[] = { h_ranges, s_ranges };

   Mat hsv, hue, saturation, mask, histimg = Mat::zeros(200, 320, CV_8UC3);
   MatND hist, backproj;

   Rect selection;
   int vmin = 10, vmax = 256, smin = 30;

   cvtColor(frame, hsv, CV_BGR2HSV);

   selection.x = pnt.x; //selected center for the area
   selection.y = pnt.y; //selected center for the area
   selection.width = 20; //selected center for the area
   selection.height = 20; //selected center for the area

   selection &= Rect(0, 0, frame.cols, frame.rows);

   int _vmin = vmin, _vmax = vmax;

   inRange(hsv, Scalar(0, smin, MIN(_vmin,_vmax)), Scalar(180, 256, MAX(_vmin, _vmax)), mask);
   hue.create(hsv.size(), hsv.depth());
   saturation.create(hsv.size(), hsv.depth());
   Mat out[] = { hue, saturation };
   int ch[] = { 0,0, 1,0};
   Mat planes[2][2];

   mixChannels(&hsv, 1, out, 2, ch, 2);

   planes[0][0] = hue; 
   planes[0][1] = saturation;

   Mat roi1(hue, selection), roi2(saturation, selection), maskroi(mask, selection);

   planes[1][0] = roi1; //selected template
   planes[1][1] = roi2; //selected template        

   calcHist(planes[1], 1, 0, maskroi, hist, 1, hdims, ranges);
   normalize(hist, hist, 0, 255, CV_MINMAX);

   calcBackProject(planes[0], 1, 0, hist, backproj, ranges);
   backproj &= mask;
   threshold( backproj, backproj, 250, 255,0 );

   return backproj;

}

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