绕另一点一个点 [英] Rotate a point around another point

问题描述

我有个任务绘制特定图形。由于这个任务，我需要在旋转45度的一些点的一部分。

I have a task to draw a specific graphic. As part of this task I need to rotate some dot's on 45 degrees.

我已经花了2天尝试计算公式，但只是无法得到它对。
我一直在寻找全国各地，包括这个特定的网站，我已经非常接近，但我仍然不存在。

I've spent already 2 days trying to calculate a formula, but just couldn't get it right. I've been searching all over the place including this particular website, I'm getting very close, but I'm still not there.

这地方是：
我需要绘制4个不同的点

Here it is: I need to draw 4 different points

我有一个特定的公式来计算有位置，这是出了问题的范围，但这里是什么我得到作为它的结果：

I have a specific formula to calculate there position, which is out of scope of the question, but here is what I'm getting as a result of it:

int radius = 576;
int diameter = radius * 2;
Point blueA = new Point(561, 273);
Point greenB = new Point(273, 561);
Point yellowC = new Point (849, 561);
Point redD = new Point (561, 849);

现在我需要在45度旋转，这点。我用下面的代码来实现它：

Now I need to rotate this dots on 45 degrees. I use the following code to achieve it:

double rotationAngle = 45;
double rotationRadians = rotationAngle * (Math.PI / 180);
int center = radius;    
result.X = (int)(Math.Cos(rotationRadians) * ((double)result.X - (double)center) - (double)Math.Sin(rotationRadians) * ((double)result.Y - center) + (double)center);
result.Y = (int)(Math.Sin(rotationRadians) * ((double)result.X - (double)center) + (double)Math.Cos(rotationRadians) * ((double)result.Y - center) + (double)center);

但是，这就是我得到：

But that's what I'm getting:

任何帮助将不胜感激

推荐答案

问题是 INT中心=半径为其设置 INT半径= 576 。因为肯定你绕应该有一个X和Y位置的点这是没有意义的。

The problem is int center = radius which you are setting int radius = 576. This doesn't make sense as surely you are rotating about a point that should have an x and y location.

给你周围的起源中心 X 和是既要为 0 不是 576 。

Given you are rotating around the origin the center x and y should both be 0 not 576.

因此，鉴于这种情况，试试这个

So, given that, try this.

/// <summary>
/// Rotates one point around another
/// </summary>
/// <param name="pointToRotate">The point to rotate.</param>
/// <param name="centerPoint">The center point of rotation.</param>
/// <param name="angleInDegrees">The rotation angle in degrees.</param>
/// <returns>Rotated point</returns>
static Point RotatePoint(Point pointToRotate, Point centerPoint, double angleInDegrees)
{
    double angleInRadians = angleInDegrees * (Math.PI / 180);
    double cosTheta = Math.Cos(angleInRadians);
    double sinTheta = Math.Sin(angleInRadians);
    return new Point
    {
        X =
            (int)
            (cosTheta * (pointToRotate.X - centerPoint.X) -
            sinTheta * (pointToRotate.Y - centerPoint.Y) + centerPoint.X),
        Y =
            (int)
            (sinTheta * (pointToRotate.X - centerPoint.X) +
            cosTheta * (pointToRotate.Y - centerPoint.Y) + centerPoint.Y)
    };
}

使用像这样。

Point center = new Point(0, 0); 
Point newPoint = RotatePoint(blueA, center, 45);

如果中心点总是很显然 0,0 则可以相应地简化功能，否则使中心点通过默认的参数可选，或者通过重载方法。你也可能会想要封装了一些可重复使用的数学到其他静态方法了。

Obviously if the center point is always 0,0 then you can simplify the function accordingly, or else make the center point optional via a default parameter, or by overloading the method. You would also probably want to encapsulate some of reusable the math into other static methods too.

例如

/// <summary>
/// Converts an angle in decimal degress to radians.
/// </summary>
/// <param name="angleInDegrees">The angle in degrees to convert.</param>
/// <returns>Angle in radians</returns>
static double DegreesToRadians(double angleInDegrees)
{
   return angleInDegrees * (Math.PI / 180);
}

/// <summary>
/// Rotates a point around the origin
/// </summary>
/// <param name="pointToRotate">The point to rotate.</param>
/// <param name="angleInDegrees">The rotation angle in degrees.</param>
/// <returns>Rotated point</returns>
static Point RotatePoint(Point pointToRotate, double angleInDegrees)
{
   return RotatePoint(pointToRotate, new Point(0, 0), angleInDegrees);
}

使用像这样。

Point newPoint = RotatePoint(blueA, 45);

最后，如果您使用的是GDI，你也可以简单地做一个 RotateTransform 。
请参阅： http://msdn.microsoft.com/en-us /library/a0z3f662.aspx

Graphics g = this.CreateGraphics();
g.TranslateTransform(blueA);
g.RotateTransform(45);

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