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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-NZ link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Drawing an arc is <i>already</i> easy, using the Canvas.Arc() method that you have already identified. </span><span style='font-size:11.0pt;font-family:Wingdings;color:#1F497D'>J</span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>You simply need to derive the values required to input to that method. </span><span style='font-size:11.0pt;font-family:Wingdings;color:#1F497D'>J</span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Given that you have the start/end points and it seems from the way you have put it that these are known to be on the arc, all you are missing is the bounding rectangle for the ellipse.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>You have the center point, so if you know the axial dimensions of the ellipse (width/height) then calculating the bounding rectangle is a simple matter of:<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><b><span style='font-size:9.0pt;font-family:"Courier New";color:#1F497D'> bound.Left := center.x – (width div 2);<o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:9.0pt;font-family:"Courier New";color:#1F497D'> bound.Top := center.y – (height div 2);<o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:9.0pt;font-family:"Courier New";color:#1F497D'> bound.Right := center.x + (width div 2);<o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:9.0pt;font-family:"Courier New";color:#1F497D'> bound.Bottom := center.y + (height div 2);<o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:9.0pt;font-family:"Courier New";color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><b><span style='font-size:9.0pt;font-family:"Courier New";color:#1F497D'> Canvas.Arc( bound.Left, bound.Top, bound.Right, bound.Bottom, start.X, start.Y, end.X, end.Y );<o:p></o:p></span></b></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>If the ellipse is (or could be) rotated then things are more complicated I think.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I forget which is the default direction for arc drawing (clockwise or counter-clockwise) but if you need to adjust that then I <i>think</i> you can either simply swap your start/end points or explicitly set the arc direction using the SetArcDirection() GDI call:<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><a href="http://msdn.microsoft.com/en-us/library/dd162961(v=VS.85).aspx">http://msdn.microsoft.com/en-us/library/dd162961(v=VS.85).aspx</a><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>If the start/end points are not actually ON the arc, then you will need to calculate the intersection of the lines defined by those points w.r.t the ellipse center. This is basic trig tho, and any number of online sources should provide the formulae for these calculations, should you need them.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> delphi-bounces@delphi.org.nz [mailto:delphi-bounces@delphi.org.nz] <b>On Behalf Of </b>Marshland Engineering<br><b>Sent:</b> Tuesday, 18 January 2011 21:03<br><b>To:</b> delphi@delphi.org.nz<br><b>Subject:</b> [DUG] Arc's<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Is there an easy way of drawing an arc ? I have center, start and end co-ordinates as XY. </span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>From what I can see, I need to look at least 16 combinations to work out the perimeter size depending in which quadrant the start and ends are in. </span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>procedure Arc(X1, Y1, X2, Y2, X3, Y3, X4, Y4: Integer);</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Use Arc to draw an elliptically curved line with the current Pen. The arc traverses the perimeter of an ellipse that is bounded by the points (X1,Y1) and (X2,Y2). The arc is drawn following the perimeter of the ellipse, counterclockwise, from the starting point to the ending point. The starting point is defined by the intersection of the ellipse and a line defined by the center of the ellipse and (X3,Y3). The ending point is defined by the intersection of the ellipse and a line defined by the center of the ellipse and (X4, Y4).</span><o:p></o:p></p></div><div><p class=MsoNormal><em><span style='font-size:7.5pt;font-family:"Arial","sans-serif";color:red'>DISCLAIMER: This electronic message together with any attachments is confidential. If you are not the intended recipient, do not copy, disclose or use the contents in any way. Please also advise us by return e-mail that you have received the message and then please destroy. Carter Holt Harvey is not responsible for any changes made to this message and / or any attachments after sending by Carter Holt Harvey. 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