带有虚线样式和大量数据点的 MSChart 折线图

Question

我正在尝试使用 C# 中的 MSChart 以虚线样式呈现折线图。我设置样式没有问题，但我有大量数据。这会导致虚线渲染出错，因为它似乎在绘制每个线段时重新启动了“破折号”序列。因此，我得到一条看起来与实线相同的线。如果我放大以使我的数据点密度降低，则虚线样式变得可见。

这对我没有好处，因为我真的需要它来保持任何缩放级别的冲刺。有没有人知道这怎么可能？对我来说它搞砸了这样的渲染似乎很奇怪......

有什么想法吗？

Answer 1

嗯，这比我预期的要麻烦得多。问题的出现是因为 MSChart 将每 2 个点之间的线作为单独的 DrawLine 调用绘制。如果整个东西都是用一个 DrawLines 调用来绘制的，那么问题就不会存在了。

因此，我想出了一种方法来处理它。

首先在 PrePaint 中存储所有“BorderWidth”，然后将它们设置为 0。这意味着 MSChart 不会绘制我的线条。

最后在 PostPaint 中，我使用我想要的虚线样式绘制线条。这提供了完美的渲染。

我确信在某些极端情况下我的代码将无法正常工作，但这应该让您对如何做到这一点有一个很好的了解：

    private List< int > mBorderWidths   = null;
    private void LineChartPrePaint( object sender, System.Windows.Forms.DataVisualization.Charting.ChartPaintEventArgs e )
    {
        if ( e.ChartElement.GetType() == typeof( System.Windows.Forms.DataVisualization.Charting.ChartArea ) )
        {
            System.Windows.Forms.DataVisualization.Charting.Chart           c   = (System.Windows.Forms.DataVisualization.Charting.Chart)e.Chart;
            System.Windows.Forms.DataVisualization.Charting.ChartArea       ca  = (System.Windows.Forms.DataVisualization.Charting.ChartArea)e.ChartElement;

            mBorderWidths   = new List<int>();
            foreach( System.Windows.Forms.DataVisualization.Charting.Series s in c.Series )
            {
                mBorderWidths.Add( s.BorderWidth );
                s.BorderWidth   = 0;
                s.ShadowOffset  = 0;
            }

            RectangleF rectF    = ca.Position.ToRectangleF();
            rectF               = e.ChartGraphics.GetAbsoluteRectangle( rectF );

            e.ChartGraphics.Graphics.FillRectangle( new SolidBrush( ca.BackColor ), rectF );
        }
        if ( e.ChartElement.GetType() == typeof( System.Windows.Forms.DataVisualization.Charting.Chart ) )
        {
            RectangleF rectF    = e.Position.ToRectangleF();
            rectF               = e.ChartGraphics.GetAbsoluteRectangle( rectF );

            e.ChartGraphics.Graphics.FillRectangle( new SolidBrush( e.Chart.BackColor ), rectF );
        }
    }

    System.Drawing.Drawing2D.DashStyle ChartToDrawingDashStyle( System.Windows.Forms.DataVisualization.Charting.ChartDashStyle cds )
    {
        switch( cds )
        {
            case System.Windows.Forms.DataVisualization.Charting.ChartDashStyle.NotSet:
            case System.Windows.Forms.DataVisualization.Charting.ChartDashStyle.Solid:
                return System.Drawing.Drawing2D.DashStyle.Solid;
            case System.Windows.Forms.DataVisualization.Charting.ChartDashStyle.Dash:
                return System.Drawing.Drawing2D.DashStyle.Dash;
            case System.Windows.Forms.DataVisualization.Charting.ChartDashStyle.DashDot:
                return System.Drawing.Drawing2D.DashStyle.DashDot;
            case System.Windows.Forms.DataVisualization.Charting.ChartDashStyle.DashDotDot:
                return System.Drawing.Drawing2D.DashStyle.DashDotDot;
            case System.Windows.Forms.DataVisualization.Charting.ChartDashStyle.Dot:
                return System.Drawing.Drawing2D.DashStyle.Dot;
        }
        return System.Drawing.Drawing2D.DashStyle.Solid;
    }

    private void LineChartPostPaint( object sender, System.Windows.Forms.DataVisualization.Charting.ChartPaintEventArgs e )
    {
        if ( e.ChartElement.GetType() == typeof( System.Windows.Forms.DataVisualization.Charting.ChartArea ) )
        {
            System.Windows.Forms.DataVisualization.Charting.Chart       c   = (System.Windows.Forms.DataVisualization.Charting.Chart)e.Chart;
            System.Windows.Forms.DataVisualization.Charting.ChartArea   ca  = (System.Windows.Forms.DataVisualization.Charting.ChartArea)e.ChartElement;

            RectangleF clipRect = e.ChartGraphics.GetAbsoluteRectangle( e.Position.ToRectangleF() );
            RectangleF oldClip  = e.ChartGraphics.Graphics.ClipBounds;
            e.ChartGraphics.Graphics.SetClip( clipRect );

            int seriesIdx   = 0;
            foreach( System.Windows.Forms.DataVisualization.Charting.Series s in c.Series )
            {
                PointF  ptFLast         = new PointF( 0.0f, 0.0f );
                List< PointF > points   = new List<PointF>();
                foreach( System.Windows.Forms.DataVisualization.Charting.DataPoint dp in s.Points )
                {
                    double dx   = (double)dp.XValue;
                    double dy   = (double)dp.YValues[0];

                    // Log the value if its axis is logarithmic.
                    if ( ca.AxisX.IsLogarithmic )
                    {
                        dx  = Math.Log10( dx );
                    }
                    if ( ca.AxisY.IsLogarithmic )
                    {
                        dy  = Math.Log10( dy );
                    }

                    dx  = e.ChartGraphics.GetPositionFromAxis( ca.Name, System.Windows.Forms.DataVisualization.Charting.AxisName.X, dx );
                    dy  = e.ChartGraphics.GetPositionFromAxis( ca.Name, System.Windows.Forms.DataVisualization.Charting.AxisName.Y, dy );

                    PointF  ptFThis         = e.ChartGraphics.GetAbsolutePoint( new PointF( (float)dx, (float)dy ) );
                    points.Add( ptFThis );
                }


                if ( points.Count > 0 )
                {
                    Pen pen = new Pen( Color.FromArgb( 255, s.Color ) );
                    pen.Width       = mBorderWidths[seriesIdx];
                    pen.DashStyle   = ChartToDrawingDashStyle( s.BorderDashStyle );
                    //pen.DashStyle = System.Drawing.Drawing2D.DashStyle.Custom;
                    //pen.DashPattern   = new float[]{ 4.0f, 4.0f, 1.0f, 3.0f, 2.0f, 3.0f };
                    pen.DashCap     = System.Drawing.Drawing2D.DashCap.Round;

                    e.ChartGraphics.Graphics.SmoothingMode  = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                    e.ChartGraphics.Graphics.DrawLines( pen, points.ToArray() );

                }
                s.BorderWidth   = mBorderWidths[seriesIdx];
            }

            e.ChartGraphics.Graphics.SetClip( oldClip );
        }
    }

我真的希望这能减轻一些人的痛苦！