Take a look at the following sample code....the part which renders
using a DashPattern is very very slow.
The same rendering using a Solid pen is hundreds of times faster.
Anyone, any idea why?

using System;
using System.Collections;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;

public class MyClass : Form
{
static internal void InitialiseGraphics(Graphics graphics)
{
// We must set these value, specifically the PixelOffsetMode,
otherwise we are getting white spaces between tiles of raster
Console.WriteLine("PageUnit: {0}", graphics.PageUnit);

graphics.PixelOffsetMode = PixelOffsetMode.None;
graphics.PageUnit = GraphicsUnit.Pixel;

graphics.Clip = new Region(new Rectangle(0, 0, 400, 400));

//graphics.SmoothingMode = SmoothingMode.None;
//graphics.InterpolationMode = InterpolationMode.NearestNeighbor;
//graphics.CompositingMode = CompositingMode.SourceOver;
//graphics.CompositingQuality = CompositingQuality.HighSpeed;
//graphics.TextRenderingHint =
System.Drawing.Text.TextRenderingHint.ClearTypeGri dFit;
}

public static void Main()
{
MyClass my = new MyClass();

my.Location = new Point(10, 10);
my.Size = new Size(500, 500);

my.Show();

Pen pen = new Pen(Color.Blue, 2);
pen.DashPattern = new float[] { 2.5F, 5.0F };
pen.DashStyle = DashStyle.Custom;

Pen pen2 = new Pen(Color.Yellow, 3);

Brush brush = new SolidBrush(Color.FromArgb(100, 0, 200, 100));

Graphics graphics = my.CreateGraphics();
InitialiseGraphics(graphics);

PointF[] points = new PointF[2];
points[0] = new PointF(-2000000, -2001000);
points[1] = new PointF(2000100, 2000000);

DateTime beg = DateTime.Now;
graphics.DrawLines(pen2, points);
DateTime end = DateTime.Now;
Console.WriteLine("Time for Pen(3): {0}", end - beg);

beg = DateTime.Now;
graphics.DrawLines(pen, points);
end = DateTime.Now;
Console.WriteLine("Time for Dashed: {0}", end - beg);


System.Threading.Thread.Sleep(2000);

}

}



The result:

Time for Pen(3): 00:00:00.0156250
Time for Dashed: 00:00:06.4375000

Because a dash pattern is hard to draw?

--
Bob Powell [MVP]
Visual C#, System.Drawing

Ramuseco Limited .NET consulting
http://www.ramuseco.com

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"Patrick van Dijk" <patrick.van.dijk (AT) gmail (DOT) com> wrote

Take a sheet of A4, take a ruler and pen, first draw a straight line, pretty
quick, now draw some dash dot same thing applies, with dash dot there's
extra steps the draw functions needs to take as you can pass in a variable
lengthed dash dot pattern etc, so it's doing more work, so takes longer.

Just verbose on Bob's reply

"Bob Powell [MVP]" <bob (AT) _spamkiller_ (DOT) bobpowell.net> wrote