Raphael.fn.canvas2dArc

gistfile1.js

var round = function(value) {
  return Math.round(value*100)/100;
};

Raphael.fn.canvas2dArc = function(x, y, radius, aStartAngle, aEndAngle, anticlockwise) {
  
  var startX, startY, endX, endY;
  var fullCircle = 2 * Math.PI;
  var startAngle = (anticlockwise || 0) ? aEndAngle : aStartAngle;
  var endAngle   = (anticlockwise || 0) ? Math.abs(fullCircle - aStartAngle) : aEndAngle;
  var diffAngle   = Math.abs(( startAngle > endAngle ) ? fullCircle - (startAngle - endAngle) : endAngle - startAngle);

  // full circle
  if ( diffAngle >= fullCircle ) {
    return this.path([
      "M", x + radius, y,
      "A", radius, radius, 0, 1, 1, x + radius * Math.cos(fullCircle), round(y + radius * Math.sin(fullCircle)) - 0.0001
    ]);
  }
  
  startX   = round(x + radius * Math.cos(startAngle));
  startY   = round(y + radius * Math.sin(startAngle));
  endX     = round(x + radius * Math.cos(endAngle));
  endY     = round(y + radius * Math.sin(endAngle));
  
  return this.path([
    "M", startX, startY,
    "A", radius, radius, 0, (diffAngle < Math.PI) ? 0 : 1, 1, endX, endY
  ]);
  
};