SvgPathSegCurveToCubic.cs :  » GUI » SharpVectorGraphics » SharpVectors » Dom » Svg » C# / CSharp Open Source

using System;
using System.Drawing;
using SharpVectors.Polynomials;

#if TEST
using NUnit.Framework;
#endif

namespace SharpVectors.Dom.Svg{
  public abstract class SvgPathSegCurvetoCubic : SvgPathSegCurveto
  {
        #region constructors
    protected SvgPathSegCurvetoCubic(SvgPathSegType type) : base(type)
    {
    }
        #endregion

        #region abstract properties
    public abstract override PointF AbsXY{get;}
    public abstract override PointF CubicX1Y1{get;}
    public abstract override PointF CubicX2Y2{get;}
        #endregion

        #region protected methods
        protected override SqrtPolynomial getArcLengthPolynomial() 
        {
            double c3x, c3y, c2x, c2y, c1x, c1y;
            PointF p1 = PreviousSeg.AbsXY;
            PointF p2 = CubicX1Y1;
            PointF p3 = CubicX2Y2;
            PointF p4 = AbsXY;
            
            // convert curve into polynomial
            c3x = -1.0*p1.X + 3.0*p2.X - 3.0*p3.X + p4.X;
            c3y = -1.0*p1.Y + 3.0*p2.Y - 3.0*p3.Y + p4.Y;

            c2x = 3.0*p1.X - 6.0*p2.X + 3.0*p3.X;
            c2y = 3.0*p1.Y - 6.0*p2.Y + 3.0*p3.Y;

            c1x = -3.0*p1.X + 3.0*p2.X;
            c1y = -3.0*p1.Y + 3.0*p2.Y;

            // build polynomial
            // dx = dx/dt
            // dy = dy/dt
            // sqrt poly = sqrt( (dx*dx) + (dy*dy) )
            return new SqrtPolynomial(
                c1x*c1x + c1y*c1y,
                4.0*(c1x*c2x + c1y*c2y),
                4.0*(c2x*c2x + c2y*c2y) + 6.0*(c1x*c3x + c1y*c3y),
                12.0*(c2x*c3x + c2y*c3y),
                9.0*(c3x*c3x + c3y*c3y)
            );
        }
        #endregion

        #region unit tests
        #if TEST
        [TestFixture]
        public abstract class CubicTests
        {
            protected SvgPathSegList segments;
            private SvgPathSegCurvetoCubic segment;

            [SetUp]
            public void SetUp()
            {
                segments = makeSegments();
                segment = getTestSegment();
            }

            [Test]
            public void TestArcLengthPolynomial()
            {
                SqrtPolynomial poly = segment.getArcLengthPolynomial();

                Assert.AreEqual(4, poly.Degree);
                Assert.AreEqual(900, poly[4]);
                Assert.AreEqual(-3600, poly[3]);
                Assert.AreEqual(279000, poly[2]);
                Assert.AreEqual(-259200, poly[1]);
                Assert.AreEqual(145800, poly[0]);
            }

            [Test]
            public void TestArcLength()
            {
                SqrtPolynomial poly = segment.getArcLengthPolynomial();
                float result1 = segment.Length;
                double result2 = Math.Floor(poly.Simpson(0, 1)*1e6)/1e6;

                Assert.AreEqual(327.877900, result1);
                Assert.AreEqual(327.877935, result2);
            }

            public abstract SvgPathSegList makeSegments();
            public abstract SvgPathSegCurvetoCubic getTestSegment();
        }
        #endif
        #endregion
  }
}