I have a task to draw a specific graphic. As part of this task I need to rotate some dot's on 45 degrees.
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.
Here it is: I need to draw 4 different points
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);
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);
But that's what I'm getting:
Any help would be much appreciated
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.
Given you are rotating around the origin the center x
and y
should both be 0
not 576
.
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)
};
}
Use like so.
Point center = new Point(0, 0);
Point newPoint = RotatePoint(blueA, center, 45);
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 the reusable math into other static methods too.
e.g.
/// <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);
}
Use like so.
Point newPoint = RotatePoint(blueA, 45);
Finally, if you are using the GDI you can also simply do a RotateTransform
.
See: http://msdn.microsoft.com/en-us/library/a0z3f662.aspx
Graphics g = this.CreateGraphics();
g.TranslateTransform(blueA);
g.RotateTransform(45);