找出两点间的角度

Question

我试图使一个图像移动到我的鼠标指针。基本上，我得到了点之间的角度，然后沿着x轴移动，通过角度的余弦，沿着y轴移动，这是角度的正弦波。

然而，我没有一个很好的方法来计算角度。我得到x的差和y的差，用Δy/Δx的arctangent，象限1的角度是正确的，但其他三个象限是错的。象限2在-1到-90度之间.象限3总是等于象限1，象限4总是象限4。有一个方程，我可以用它从1-360度求出两点之间的夹角吗？。

注意:我不能使用atan2()，也不知道向量是什么。

Answer 1

关于atan2的答案是正确的。作为参考，这里是划痕块形式的atan2：

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Answer 2

// This working code is for Windows HDC mouse coordinates gives the angle back that is used in Windows. It assumes point 1 is your origin point
// Tested and working on Visual Studio 2017 using two mouse coordinates in HDC.
//
// Code to call our function.
float angler = get_angle_2points(Point1X, Point1Y, Point2X, Point2Y);


// Takes two window coordinates (points), turns them into vectors using the origin and calculates the angle around the x-axis between them.
// This function can be used for any HDC window. I.e., two mouse points.
float get_angle_2points(int p1x, int p1y, int p2x,int p2y)
{
    // Make point1 the origin, and make point2 relative to the origin so we do point1 - point1, and point2-point1,
    // Since we don’t need point1 for the equation to work, the equation works correctly with the origin 0,0.
    int deltaY = p2y - p1y;
    int deltaX = p2x - p1x; // Vector 2 is now relative to origin, the angle is the same, we have just transformed it to use the origin.

    float angleInDegrees = atan2(deltaY, deltaX) * 180 / 3.141;

    angleInDegrees *= -1; // Y axis is inverted in computer windows, Y goes down, so invert the angle.

    //Angle returned as:
    //                      90
    //            135                45
    //
    //       180          Origin           0
    //
    //
    //           -135                -45
    //
    //                     -90


    // The returned angle can now be used in the C++ window function used in text angle alignment. I.e., plf->lfEscapement = angle*10;
    return angleInDegrees;
}

Answer 3

如果无法直接使用atan2()，则可以自行实现其内部计算：

atan2(y,x) =    atan(y/x)   if x>0
                atan(y/x) + π   if x<0 and y>0
                atan(y/x) - π   if x<0 and y<0