c++ - Calculating the angle between Points -

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working c++ , opencv

i trying calculate angle between 2 points.....i have 2d plane changing center point of bounding box, if center point in frame 1 has changed location in frame 2 need find angle of these 2 points.

here example of trying do:

enter image description here

can suggest way of working out.......? kind of mathematical solution or perhaps c++ function.

use dot product:

v1.v2 = v1.x * v2.x + v1.y * v2.y  v1.v2 = |v1| * |v2| * cos(theta) ---------------------------------+                                  |                                  +-->  theta = acos(v1.v2 / |v1|*|v2|)

a sample code is:

float anglebetween(const point &v1, const point &v2) {     float len1 = sqrt(v1.x * v1.x + v1.y * v1.y);     float len2 = sqrt(v2.x * v2.x + v2.y * v2.y);      float dot = v1.x * v2.x + v1.y * v2.y;      float = dot / (len1 * len2);      if (a >= 1.0)         return 0.0;     else if (a <= -1.0)         return pi;     else         return acos(a); // 0..pi }

it calculates angle between v1 , v2 below image

enter image description here


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