DrawTool画笔之图形笔

/// <summary>    /// 图形笔    /// </summary>    public class ImageStroke : Stroke    {        PRivate string imageFile_;        private System.Windows.Media.ImageSource imageSource_;        private Point curPoint;        public ImageStroke(System.Windows.Input.StylusPointCollection points, DrawingAttributes da, string file)            : base(points, da)        {            this.imageFile_ = file;            this.imageSource_ = new System.Windows.Media.Imaging.BitmapImage(new Uri( this.imageFile_));        }        protected override void DrawCore(System.Windows.Media.DrawingContext drawingContext, DrawingAttributes drawingAttributes)        {            double num = drawingAttributes.Width + 20.0;            System.Windows.Media.StreamGeometry streamGeometry = new System.Windows.Media.StreamGeometry();            using (System.Windows.Media.StreamGeometryContext streamGeometryContext = streamGeometry.Open())            {                streamGeometryContext.BeginFigure((Point)base.StylusPoints[0], false, false);                drawingContext.DrawImage(this.imageSource_, new Rect(((Point)base.StylusPoints[0]).X - num / 2.0, ((Point)base.StylusPoints[0]).Y - num / 2.0, num, num));                this.curPoint = (Point)base.StylusPoints[0];                foreach (System.Windows.Input.StylusPoint current in base.StylusPoints)                {                    ImageStroke.DrawImage(ref this.curPoint, (Point)current, num, drawingContext, this.imageSource_);                }            }        }        public static double GetDistance(Point a, Point b)        {            return System.Math.Abs(Point.Subtract(a, b).Length);        }        public static Point GetPointBetween(Point a, Point b, double len)        {            Vector vector = Point.Subtract(a, b);            vector.Normalize();            vector = Vector.Multiply(vector, len);            return Point.Subtract(a, vector);        }        public static void DrawImage(ref Point a, Point b, double width, System.Windows.Media.DrawingContext drawingContext, System.Windows.Media.ImageSource imageSource)        {            for (double distance = ImageStroke.GetDistance(a, b); distance >= width; distance = ImageStroke.GetDistance(a, b))            {                Point pointBetween = ImageStroke.GetPointBetween(a, b, width);                drawingContext.DrawImage(imageSource, new Rect(pointBetween.X - width / 2.0, pointBetween.Y - width / 2.0, width, width));                a = pointBetween;            }        }    }