c++ - Find X and Y coordinates of point in relation to the whole image -

i trying find nose tip landmark inside 2d image. it's not working 100% correct, first approach satisfy me.

vector<rect> noses; vector<rect> faces; vector<rect> eyes; mat frame_gray; mat matched_frame; //frame matched face mat gray; rect region_of_interest;  cvtcolor(frame, frame_gray, color_bgr2gray);  face_cascade.detectmultiscale(frame_gray, faces, 1.1, 2, 0 | cascade_scale_image, size(30, 30));  (int = 0; < faces.size(); i++) {         point pt1(faces[i].x, faces[i].y); // display detected faces on main window - live stream camera         point pt2((faces[i].x + faces[i].height), (faces[i].y + faces[i].width));         rectangle(frame, pt1, pt2, scalar(255,0 , 0), 2, 8, 0);          cvtcolor(frame, frame_gray, color_bgr2gray);         equalizehist( frame_gray, frame_gray );          //nose tip detection         rect noseroi1;         noseroi1.x = (faces[i].x);         noseroi1.y = faces[i].y + (faces[i].height/2.5);         noseroi1.width = (faces[i].width);         noseroi1.height = (faces[i].height/2.8);          point ptnosex(noseroi1.x, noseroi1.y);         point ptnosey(noseroi1.x+noseroi1.width, noseroi1.y+noseroi1.height);         //rectangle around region of interest concentrated on nose         rectangle(frame, ptnosex,ptnosey, scalar(0,255,255), 2, 2, 0);          mat image_roi_nose = frame(noseroi1);          nose_cascade.detectmultiscale(image_roi_nose, noses, 1.1, 2, 0 | cascade_scale_image, size(40, 30));          (int = 0; < noses.size(); i++)         {             region_of_interest.x = noses[i].x;             region_of_interest.y = noses[i].y;             region_of_interest.width = (noses[i].width);             region_of_interest.height = (noses[i].height);              matched_frame = frame(region_of_interest);              cvtcolor(matched_frame, gray, cv_bgr2gray);              point pt1(noses[i].x, noses[i].y);             point pt2((noses[i].x + noses[i].height), (noses[i].y + noses[i].width));             rectangle(image_roi_nose, pt1, pt2, scalar(0, 255, 0), 2, 8, 0);              int x1 = noses[i].x + (noses[i].height/2);             int y1 = noses[i].y + (noses[i].width/2);               circle(image_roi_nose, point(x1, y1), 2, cv_rgb(255,0,0),2, 8, 0);         } 

this code finds nose tip, returns me x1 , y1 in relation mat image_roi_nose, how can calculate coordinates of point in relation whole image?? if question unclear, please let me know try explain more details.

thank help!

x = x1 + noseroi1.x; y = y1 + noseroi1.y;