VerticalBarsPainter.cs

using SkiaSharp;
 
namespace Waher.Script.Graphs.Functions.Plots
{
    public class VerticalBarsPainter : SingleColorGraphPainter, IPainter2D
    {
        public void DrawGraph(SKCanvas Canvas, SKPoint[] Points, object[] Parameters, SKPoint[] PrevPoints, object[] PrevParameters,
            DrawingArea DrawingArea)
        {
            SKPaint Brush = null;
            SKPath Path = null;
 
            try
            {
                Brush = new SKPaint()
                {
                    Color = Graph.ToColor(Parameters[0]),
                    Style = SKPaintStyle.Fill
                };
                Path = new SKPath();
 
                int Count = DrawingArea.XLabelPositions?.Count ?? Points.Length;
                float HalfBarWidth = (DrawingArea.Width - Count) * 0.45f / Count;
                float x0, y0, x1, y1;
                int i, c;
 
                if (!(PrevPoints is null))
                {
                    if ((c = PrevPoints.Length) != Points.Length)
                        PrevPoints = null;
                    else
                    {
                        for (i = 0; i < c; i++)
                        {
                            if (PrevPoints[i].X != Points[i].X)
                            {
                                PrevPoints = null;
                                break;
                            }
                        }
                    }
                }
 
                int MinX = DrawingArea.OffsetX;
                int MaxX = DrawingArea.OffsetX + DrawingArea.Width;
 
                i = 0;
                foreach (SKPoint Point in Points)
                {
                    x0 = Point.X - HalfBarWidth + 1;
                    y0 = Point.Y;
                    x1 = Point.X + HalfBarWidth - 1;
                    y1 = !(PrevPoints is null) ? PrevPoints[i++].Y : DrawingArea.OrigoY;
 
                    if (x0 < MinX)
                        x0 = MinX;
 
                    if (x1 > MaxX)
                        x1 = MaxX;
 
                    Canvas.DrawRect(new SKRect(x0, y0, x1, y1), Brush);
                }
 
                Canvas.DrawPath(Path, Brush);
            }
            finally
            {
                Brush?.Dispose();
                Path?.Dispose();
            }
        }
 
    }
}