I'm kind of confused by your question. Do you want a circle with a circumference of 1px or a circle with a 1px border?<BR><BR>The former sounds difficult, but for the latter, you can use the ...
MATHEWS, G. A Triangle that gives the Area and Circumference of any Circle, and the Diameter of a Circle equal in Area to any given Square. Nature 93, 110 (1914 ...