Comments on: A cool page explaining circle drawing algorithms

By: Dave Johansen

Dave Johansen — Mon, 17 Aug 2009 20:08:54 +0000

@ReadOnly

The odd sized diameter is more a result of the definition of the circle (center with a radius that are both integers) than the algorithm itself. But the main point is that these algorithms were made back when computation resources were at a premium and being able to draw a good looking circle with just integer operations was a necessity.

Also, the link from the article appears to be dead, so here’s a related article on wikipedia:
http://en.wikipedia.org/wiki/Midpoint_circle_algorithm

By: Tam Hanna

Tam Hanna — Fri, 19 Jan 2007 07:47:07 +0000

Hi Ben,
I did that – but it isn’t enough for me any more=).

You will see why I need the new algorithm very soon – in fact, send me an email and I will show you now!

Best regards
Tam Hanna

By: Ben Combee

Ben Combee — Thu, 18 Jan 2007 17:20:51 +0000

Actually, if you only need a circle, you can use WinDrawRectangle, like so

RectangleType r = { 10, 10, 100, 100 };
WinDrawRectangle(&r, 50);

The second parameter is the radius of the circle placed at each corner. This would draw a circle that’s centered at 60,60 of radius 50.

This isn’t useful for ellipses, but for circles it works nicely.

By: ReadOnly

ReadOnly — Thu, 18 Jan 2007 15:53:36 +0000

The demo code only seems to support diameters in odd number of pixels.
I haven’t taken the time to analyze the approach for validity with even count diameters.
Obviously it could be adapted, if this is indeed a shortcoming.