double getRotateAngle(double x1, double y1, double x2, double y2) {
const double epsilon = 1.0e-6; const double nyPI = acos(-1.0); double dist, dot, degree, angle; // normalize dist = sqrt( x1 * x1 + y1 * y1 ); x1 /= dist; y1 /= dist; dist = sqrt( x2 * x2 + y2 * y2 ); x2 /= dist; y2 /= dist; // dot product dot = x1 * x2 + y1 * y2; if ( fabs(dot-1.0) <= epsilon ) angle = 0.0; else if ( fabs(dot+1.0) <= epsilon ) angle = nyPI; else {
double cross; angle = acos(dot); //cross product cross = x1 * y2 - x2 * y1; // vector p2 is clockwise from vector p1 // with respect to the origin (0.0) if (cross < 0 ) {
angle = 2 * nyPI - angle; } } degree = angle * 180.0 / nyPI; return degree; } 版权声明：本文内容由互联网用户自发贡献，该文观点仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请联系我们举报，一经查实，本站将立刻删除。
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