Draw an arrow with big cap

you can write your own little routine.

I just wrote up my own DrawArrow routine:

private void DrawArrow(Graphics g, PointF ArrowStart, PointF ArrowEnd, Color ArrowColor, int LineWidth, int ArrowMultiplier)
{
    //create the pen
    Pen p = new Pen(ArrowColor, LineWidth);

    //draw the line
    g.DrawLine(p, ArrowStart, ArrowEnd);

    //determine the coords for the arrow point

    //tip of the arrow
    PointF arrowPoint = ArrowEnd;

    //determine arrow length
    double arrowLength = Math.Sqrt(Math.Pow(Math.Abs(ArrowStart.X - ArrowEnd.X), 2) +
                                   Math.Pow(Math.Abs(ArrowStart.Y - ArrowEnd.Y), 2));

    //determine arrow angle
    double arrowAngle = Math.Atan2(Math.Abs(ArrowStart.Y - ArrowEnd.Y),Math.Abs(ArrowStart.X - ArrowEnd.X));

    //get the x,y of the back of the point

    //to change from an arrow to a diamond, change the 3
    //in the next if/else blocks to 6

    double pointX, pointY;
    if (ArrowStart.X > ArrowEnd.X)
    {
        pointX = ArrowStart.X - (Math.Cos(arrowAngle) * (arrowLength - (3 * ArrowMultiplier)));
    }
    else
    {
        pointX = Math.Cos(arrowAngle) * (arrowLength - (3 * ArrowMultiplier)) + ArrowStart.X;
    }

    if (ArrowStart.Y > ArrowEnd.Y)
    {
        pointY = ArrowStart.Y - (Math.Sin(arrowAngle) * (arrowLength - (3 * ArrowMultiplier)));
    }
    else
    {
        pointY = (Math.Sin(arrowAngle) * (arrowLength - (3 * ArrowMultiplier))) + ArrowStart.Y;
    }

    PointF arrowPointBack = new PointF((float)pointX, (float)pointY);

    //get the secondary angle of the left tip
    double angleB = Math.Atan2((3 * ArrowMultiplier), (arrowLength - (3 * ArrowMultiplier)));

    double angleC = Math.PI * (90 - (arrowAngle * (180 / Math.PI)) - (angleB * (180 / Math.PI))) / 180;

    //get the secondary length
    double secondaryLength = (3 * ArrowMultiplier)/Math.Sin(angleB);

    if (ArrowStart.X > ArrowEnd.X)
    {
        pointX = ArrowStart.X - (Math.Sin(angleC) * secondaryLength);
    }
    else
    {
        pointX = (Math.Sin(angleC) * secondaryLength) + ArrowStart.X;
    }

    if (ArrowStart.Y > ArrowEnd.Y)
    {
        pointY = ArrowStart.Y - (Math.Cos(angleC) * secondaryLength);
    }
    else
    {
        pointY = (Math.Cos(angleC) * secondaryLength) + ArrowStart.Y;
    }

    //get the left point
    PointF arrowPointLeft = new PointF((float)pointX, (float)pointY);

    //move to the right point
    angleC = arrowAngle - angleB;

    if (ArrowStart.X > ArrowEnd.X)
    {
        pointX = ArrowStart.X - (Math.Cos(angleC) * secondaryLength);
    }
    else
    {
        pointX = (Math.Cos(angleC) * secondaryLength) + ArrowStart.X;
    }

    if (ArrowStart.Y > ArrowEnd.Y)
    {
        pointY = ArrowStart.Y - (Math.Sin(angleC) * secondaryLength);
    }
    else
    {
        pointY = (Math.Sin(angleC) * secondaryLength) + ArrowStart.Y;
    }

    PointF arrowPointRight = new PointF((float)pointX,(float)pointY);

    //create the point list
    PointF[] arrowPoints = new PointF[4];
    arrowPoints[0] = arrowPoint;
    arrowPoints[1] = arrowPointLeft;
    arrowPoints[2] = arrowPointBack;
    arrowPoints[3] = arrowPointRight;

    //draw the outline
    g.DrawPolygon(p, arrowPoints);

    //fill the polygon
    g.FillPolygon(new SolidBrush(ArrowColor), arrowPoints);
}

to test it, I added a panel and two textboxes to a form and added two simple mouse events:

PointF mouseStart;
PointF mouseEnd;
private void panel1_MouseDown(object sender, MouseEventArgs e)
{
    mouseStart = new PointF(e.X, e.Y);
}
private void panel1_MouseUp(object sender, MouseEventArgs e)
{
    mouseEnd = new PointF
(e.X, e.Y);
    panel1.CreateGraphics().Clear(Form1.DefaultBackColor);
    DrawArrow(panel1.CreateGraphics(), mouseStart, mouseEnd, Color.Black,
              Convert.ToInt16(txtLineWidth.Text), Convert.ToInt16(txtArrowMultiplier.Text));
}

worked like a charm. You can change the line width or the size of the arrow independently.

[Modified: changed from Point to PointF for slightly more accurate points, also included a comment on how to change from an arrow to a diamond...(requires changing the code that calculates the arrowPointBack)]

Pen p = new Pen(Color.Black, 10);
     p.StartCap = LineCap.Round;
     p.EndCap = LineCap.ArrowAnchor;
     g.DrawLine(p, 30, 30, 80, 30);
     p.Dispose();

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