svg: center of path

Question

Hi

I'm trying to draw a label on a polygon of an svg file. The problem I'm facing is to find out roughly the center of this polygon to place the label, as the path's coordinates are in svg format and need to be parsed. Is there an easier way to determine the center of an svg polygon (maybe someone can point out a javascript library or a snippet)? I'm using Raphael javascript library to manipulate the svg, but it doesn't seem to go beyond the standard svg functionality.

Answer 1

The simplest thing you could try doing is to calculate the center by taking the average of all the points in the polygon. It should work for all but the most irregular of polygons. I've used the same algorithm to good effect in my programs.

Best of luck.

Answer 2

You could try the following approximation for doing something similar to the polygon suggestion, based on SVG DOM methods:

var totalPathLength = pathelm.getTotalLength();
var step = totalPathLength / 100;
for(var dist=0; dist < totalPathLength; dist+=step)
{
  var pt = pathelm.getPointAtLength(dist);
  addToAverage(pt.x, pt.y);
}

I think the simplest approach is to use the center of the path element's boundingbox (pathelm.getBBox()), that's simpler than the polygon suggestion.