c++ - OpenCV triangle detection -

there following working method find possible squares in image. suggestions how can change account triangles instead?

static void getsquares(const mat& image, vector<vector<point>>& triangles) { squares.clear();  mat pyr, timg, gray0(image.size(), cv_8u), gray;  pyrdown(image, pyr, size(image.cols/2, image.rows/2)); pyrup(pyr, timg, image.size()); vector<vector<point> > contours;  int planes = 1; int canny = 0;  if (accuracy) {     planes = 4;     canny = 1; }  (int c = 0; c < planes; c++) {     int ch[] = {c, 0};     mixchannels(&timg, 1, &gray0, 1, ch, 1);      (int l = 0; l < n; l++) {         if (l == 0 && canny == 1) {             canny(gray0, gray, 0, thresh, 5);             dilate(gray, gray, mat(), point(-1,-1));         } else gray = gray0 >= (l+1)*255/n;          findcontours(gray, contours, cv_retr_list, cv_chain_approx_simple);          vector<point> approx;          (size_t = 0; < contours.size(); i++) {             approxpolydp(mat(contours[i]), approx, arclength(mat(contours[i]), true)*0.02, true);              if(approx.size() == 4 && fabs(contourarea(mat(approx))) > 1000 && iscontourconvex(mat(approx))) {                 double maxcosine = 0;                  (int j = 2; j < 5; j++) {                     double cosine = fabs(angle(approx[j%4], approx[j-2], approx[j-1]));                     maxcosine = max(maxcosine, cosine);                 }                  if (maxcosine < tolerance) squares.push_back(approx);             }         }     } } 

}

any appreciated, otherwise if can suggestion approach.

regards, c.

at least need change

approx.size() == 4 

to

approx.size() == 3