UVtools/UVtools.Core/Slicer/SliceLine.cs

/*
 *                     GNU AFFERO GENERAL PUBLIC LICENSE
 *                       Version 3, 19 November 2007
 *  Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
 *  Everyone is permitted to copy and distribute verbatim copies
 *  of this license document, but changing it is not allowed.
 */
using System;
using System.Collections.Generic;
using System.Drawing;

namespace UVtools.Core.Slicer
{
    public class SliceLine : List<PointF>
    {
        private PointF _normal;

        public PointF Normal
        {
            get => _normal;
            set => _normal = CalculateNormal(value);
        }

        public PointF CalculateNormal(PointF normal = default)
        {
            if (!Validate())
                throw new InvalidOperationException("Can't calculate Normal without points set");

            if (normal == PointF.Empty)
                normal = _normal;
            if (normal == PointF.Empty)
                throw new InvalidOperationException("Can't calculate Normal without a starting point");

            // calculate normal slopes 
            var dX = this[0].Y - this[1].Y;
            var dY = this[0].X - this[1].X;
            // determine normal direction
            var xDir = normal.X >= 0 ? 1 : -1;
            var yDir = normal.Y >= 0 ? 1 : -1;
            // check for delta 0 in either direction
            if (dX == 0 && dY == 0)
                return new PointF(0, 0);
            if (dX == 0)
                return new PointF(0, yDir);
            if (dY == 0)
                return new PointF(xDir, 0);

            // if there aren't any zeroes, calculate the hypotenuse
            var hypotenuse = (float)Math.Sqrt((dX * dX) + (dY * dY));
            // use cross-multiplication and solve for x & y to find normal values where hypotenuse == 1
            dX = Math.Abs(dX / hypotenuse) * xDir;
            dY = Math.Abs(dY / hypotenuse) * yDir;
            return new PointF(dX, dY);
        }

        public bool Validate()
        {
            return Count == 2;
        }
    }
}