Seems to be quite easy question but I have no idea.
I want to draw a line with an arrow head. However, I couldn't find any method except below one.
Can you let me know how to do it?
The routine that I posted above doesn't account for pen size. For a one or two point pen size it won't be noticeable, but for a large pen size the arrowheads won't look good. Rather than leave things half done, I revised the routine to compensate for pen size, and while I was at it, I decided to include several arrowhead styles. A new property mArrowType has a range of 0..3 and the corresponding styles are:
0 - Open style (like the one given by Eugene Dakin)
1 - Closed triangle
2 - Filled triangle
3 - Filled polygon (sharp point arrowhead)
Public Sub DrawArrow(extends g As Graphics, x1 As Double, y1 As Double, x2 As Double, y2 As Double) 'Draw a line with arrowhead at the end 'Calling parameters are the same as for DrawLine 'Arrowhead parameters are determined by properties arrowLength and arrowAngle ' '*** Revised to compensate for large pen sizes ' const deg2halfrad = 0.008726646259972 'Get angle of line dim aLine As Double = ATan2(y2-y1,x2-x1) 'calculate angle of arrowhead lines dim ahLineA As Double = aLine-mArrowAngle*deg2halfrad dim ahLineB As Double = aLine+arrowAngle*deg2halfrad 'calculate x and y coordinates of the arrowhead points dim ahLineAx As Double = x2-mArrowLength*cos(ahLineA) dim ahLineBx As Double = x2-mArrowLength*cos(ahLineB) dim ahLineAy As Double = y2-mArrowLength*sin(ahLineA) dim ahLineBy As Double = y2-mArrowLength*sin(ahLineB) 'Pen size adjustment dim dPH as Double = g.PenHeight/2 dim dPW as Double = g.PenWidth/2 dim poly() As Double =Array(0,x2+dPW,y2+dPH,ahLineAx+dPW,ahLineAy+dPH,ahLineBx+dPW,ahLineBy+dPH) if mArrowType=0 then 'Draw the principal line g.DrawLine(x1,y1,x2,y2) Else 'Draw the principal line (only to the base of the arrowhead) g.DrawLine(x1,y1,(ahLineAx+ahLineBx)/2,(ahLineAy+ahLineBy)/2) end if if mArrowType<3 then 'Draw two line segments for arrowhead g.DrawLine(ahLineAx,ahLineAy,x2,y2) g.DrawLine(ahLineBx,ahLineBy,x2,y2) end if if mArrowType=1 or mArrowType=2 then 'Add baseline for triangle arrowhead g.DrawLine(ahLineAx,ahLineAy,ahLineBx,ahLineBy) end if if mArrowType=2 or mArrowType=3 then 'Fill the arrowhead g.FillPolygon(poly) end if End Sub