RMath.cs

using Microsoft.Xna.Framework;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Rampastring.XNAUI
{
    /// <summary>
    /// Contains static vector math functions.
    /// </summary>
    public static class RMath
    {
        /// <summary>
        /// Returns the angle / direction of a vector in radians.
        /// </summary>
        /// <param name="vector">The vector.</param>
        public static float AngleFromVector(Vector2 vector)
        {
            return (float)Math.Atan2(vector.Y, vector.X);
        }

        /// <summary>
        /// Creates and returns a new vector with the given length and angle.
        /// </summary>
        /// <param name="length">The length of the vector.</param>
        /// <param name="angle">The angle of the vector.</param>
        public static Vector2 VectorFromLengthAndAngle(float length, float angle)
        {
            return new Vector2(length * (float)Math.Cos(angle), length * (float)Math.Sin(angle));
        }

        public static Color MultiplyAlpha(Color color)
        {
            return new Color((color.A * color.R) / 255,
                (color.A * color.G) / 255,
                (color.A * color.B) / 255,
                color.A);
        } 
    }
}