Geek Answers Handbook

MSChart line chart with dotted style and lots of data points.

I am trying to display a line graph using MSChart from C # with a dashed style in a line. I have no problem setting the style, but I have a lot of data. This causes the dashed rendering to be erroneous, as it seems to restart the dash sequence when it draws each line segment. This way I get a line that looks like a solid line. If I scale so that the density of data points decreases, then the dashed style becomes noticeable.

This is not good for me, since I really need it to lose any zoom level. Are there any ideas as to how this is possible? It seems strange that I like it, how it is for me ...

Any thoughts?

+4
source share
1 answer

Well, it has turned into something more than I expected. The problem arises because MSChart draws a line between every two points as a separate DrawLine call. If all things were drawn with a single DrawLines call, the problem would not exist.

As such, I came up with a way to process the drawing.

Firstly, in PrePaint, I save all the "BorderWidth" before setting them to 0. This means that MSChart is not drawing my lines.

Finally, in PostPaint, I draw the lines using the dash style I want. This gives perfect rendering.

I'm sure there are some edge cases for which my code will not work, but this should give you a good idea on how to do this:

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 ); } }

I really hope this saves someone the pain!

+6
source

More articles:


All Articles