It should work, so perhaps you can make a little test sketch to illustrate your issue.

ok, I'm very sorry, wrong description of the issue:
without the createGraphics() there is a sort of circle to be displayed. this worked pretty well, but using this, there are only many points, outlining the circle, not a single line.

This is pretty much what it does:

      canvas.strokeWeight(lineWeight); // is 0.075 by default
      canvas.noFill();
      canvas.beginShape();
      canvas.curveVertex(x[formResolution-1]+centerX, y[formResolution-1]+centerY);  // some points, approxomately forming a circle
      for (int i=0; i<formResolution; i++){
        canvas.curveVertex(x[i]+centerX, y[i]+centerY);
      }
      canvas.curveVertex(x[0]+centerX, y[0]+centerY);
      canvas.curveVertex(x[1]+centerX, y[1]+centerY);
      canvas.endShape();

EDIT: just tried strokeWeight(1) and now there's pretty much of a line, but it would look so much better with 0.075 (it's a sort of painting programm)
Maybe that's because the canvas object is "over" the "normal" stage..? Does anybody have an idea how to solve this issue? strokeWeight(1) is also possible, but it kinda sucks :/

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Capable of English, German, French, Russian and Latin, but simple languages like AS3 or Processing are absolutely killing me!