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# How to get Length of Graphics.DrawLines (Points) in c#

Posted on 2008-11-19
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Hi,

oGraphics = e.Gragpics
Point[] pntLines = new Point{(323,449), (324, 449), (325, 448), (327,444), (327,443) }
oGraphics.DrawLines(oPen, pntLines);
oGraphics.DrawString("TestLine", Font,  Brushes.Red,  MiddleLineofPntLines?????)

How can get exactly middle of Point of pntLines.

Thanks..

0
Question by:narlasridhar
• 2

LVL 13

Expert Comment

ID: 22993855
BTW I think you have used the System.Windows.Shapes.Polygon class accordingly with the Gragpics.DrawPolygon method to draw this shape. With this Polygon class you'll get some helpful properties like Height or Width...
http://msdn.microsoft.com/en-us/library/system.drawing.graphics.drawpolygon.aspx
http://msdn.microsoft.com/en-us/library/system.windows.shapes.polygon.aspx
Anyway, as far as I know this is not a C# problem but a mathematical issue. I think you have to calculate it by yourself. I suppose that you can calculte the average X coordinates and the average of Y coordinates, don't you ?
0

LVL 11

Accepted Solution

jgordos earned 500 total points
ID: 22995923
You're asking how to compute the centroid.

This sounds like a homework problem, so i can't directly answer the "how"... but I can provide some tips...

The center of a polygon is the mean of all the X,Y coordinates...

Check the wikipedia regarding CENTROID

But, to compute the mean, do the following

For all the X in the list, sum the values...
For all the Y in the list, sum the values...
Divide by the number of point pairs in the list...

-john

0

Author Comment

ID: 23003102
hi igordos,

Thanks verymuch helping this solution.   Still i am looking for a Trigonometry function to do this in .net
The way i did....

Assuming strait line from minimum point to maximum point.  and calculating the  middle point by following formula.

(x1 - X-max point, x2  - X-Mini Point, y1 - Y-MaxPoint, y2 - Y-Miniumum Point ) in the array...
so MiddlePoint = ((x1-x2) / 2 + x1, (y1-y2) / 2)
-------------------------E x a m p l e ---------------------------------------------------------------------------
Point MinPoint = arrPoints[0];
Point MaxPoint = arrPoints[arrPoints.Length - 1];
Point MiddlePoint = new Point((int)(MaxPoint.X - MinPoint.X) / 2 + MinPoint.X,
(int)(MaxPoint.Y - MinPoint.Y) / 2 + MinPoint.Y);

Point mMaxPoint = new Point(0, 0), mMinPoint = new Point(0, 0), mMidPoint = new Point(0, 0);
int a = 0;
for (int i = 0; i < arrPoints.Length; i++)
{
if (arrPoints[i].X < MiddlePoint.X && i != arrPoints.Length - 2)
continue;
else
{
if (a == 0)
{
mMinPoint = arrPoints[i - 1];
a++;
}
else
{
mMaxPoint = arrPoints[i - 1];
mMidPoint = new Point((int)(mMaxPoint.X - mMinPoint.X/2 +  mMinPoint.X) ,
(int)(mMaxPoint.Y - mMinPoint.Y)/2 + mMinPoint.Y);
break;
}
}
}

Graphics g = pictureBox1.CreateGraphics();
g.DrawLines(new Pen(Brushes.Red), arrPoints);
g.DrawString("Test", this.Font, new SolidBrush(Color.Tomato), mMidPoint);

--------------------------------------

0

LVL 11

Expert Comment

ID: 23150976
I have no idea why you're closing it.

Can you supply some details?
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