C# GDI: Union/Outline of Overlapping Ellipses

Banging my head on the wall with this one...

Google searches so far null...

I have a ton of over lapping circles in a mapping program...they represent radar ranges for installations such as fixed operating bases, strategic facilities, anti-aircraft assets...

Most if not all overlap one or many of their bretheren...some may stand alone...Imagine an outlying installation with limited range...

I am trying to draw the UNION of the aggregated collection of circle objects...technically ellipses boun开发者_StackOverflow社区d by rectangles...

I am trying to draw the outside boundary of the air defense system...I want to eliminate all drawing of the portion of the child ellipses that fall within that outer boundry...

If an outlying station is standing alone so to speak it should be drawn as a simple circle...

Should I link a picture?

What the heck here it is...image is a bit big so I linked it

image 1024x1024

What I want to draw is union outline of the British and then of the Germans...

So far I can't figure out how to this in C# GDI...

I Do not want to fill the path using the Winding Mode Flag...I want to Draw the OUTLINE..

Any help greatly appreciated...

Oneway

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Create a new image, render the circles in solid colour to that area, then overlay that image on your map at, say, 50% opacity.

Alternatively, run an edge detect on that solid-colour image to find the overall outline.