绘制旋转矩形

Question

So I'm writting a function that takes a point and rotates it around another point at a certain angle, so when I draw a rectangle, I want that rectangle to be rotated as well,but it's distorted.I'm also drawing two colored rectangles, one without rotation and one rotated by the angle provided, like in this picture:

The purple outline should look like the red one. This is the code for the rotation

 double d2r(double d)
        {
            return (d / 180.0) * ((double)M_PI);
        }

 double sind(double x) 
        {

            return std::sin(d2r(x));
        }


 double cosd(double x) 
        {
            return std::cos(d2r(x));
        }


std::pair<double, double> rotate_around(double x, double y, double o_x, double o_y, double angle)
{


    x = o_x + (x - o_x) * cosd(angle) - (y - o_y) * sind(angle);
    y = o_y + (y - o_y) * cosd(angle) + (x - o_x) * sind(angle);

    return std::pair<double, double>(x, y);

}

The function rotate_around is called with the following parameters (original x, original y , middle x of the rectangle, middle y of the rectangle, angle of the rectangle)

Can someone please tell me what am I doing wrong here?

Answer 1

x-= o_x; y-= o_y;
angle= d2r(angle);
double c= std::cos(angle), s= std::sin(angle);

return std::pair<double, double>(o_x + x * c - y * s, o_y + y * c + x * s);

will work.