http://www.jasondavies.com/wordcloud/ 中的一段代码

Converts svg to png.js

// Converts a given word cloud to image/png.
function downloadPNG() {
  var canvas = document.createElement("canvas"),
      c = canvas.getContext("2d");
  canvas.width = w;
  canvas.height = h;
  c.translate(w >> 1, h >> 1);
  c.scale(scale, scale);
  words.forEach(function(word, i) {
    c.save();
    c.translate(word.x, word.y);
    c.rotate(word.rotate * Math.PI / 180);
    c.textAlign = "center";
    c.fillStyle = fill(word.text.toLowerCase());
    c.font = word.size + "px " + word.font;
    c.fillText(word.text, 0, 0);
    c.restore();
  });
  d3.select(this).attr("href", canvas.toDataURL("image/png"));
}