audiogram/audiogram/draw-frames.js

var fs = require("fs"),
  path = require("path"),
  Canvas = require("../vendor/canvas"),
  queue = require("d3").queue;

function drawFrames(renderer, options, cb) {
  var frameQueue = queue(10),
    canvases = [];

  for (var i = 0; i < 10; i++) {
    canvases.push(new Canvas(options.width, options.height));
  }

  for (var i = 0; i < options.numFrames; i++) {
    frameQueue.defer(drawFrame, i);
  }

  frameQueue.awaitAll(cb);

  function drawFrame(frameNumber, frameCallback) {
    var canvas = canvases.pop(),
      context = canvas.getContext("2d");

    renderer.drawFrame(context, {
      caption: options.caption,
      citation: options.citation,
      label: options.label,
      waveform: options.waveform[frameNumber],
      frame: frameNumber
    });

    canvas.toBuffer(function(err, buf) {
      if (err) {
        return cb(err);
      }

      fs.writeFile(
        path.join(options.frameDir, zeropad(frameNumber + 1, 6) + ".png"),
        buf,
        function(writeErr) {
          if (writeErr) {
            return frameCallback(writeErr);
          }

          if (options.tick) {
            options.tick();
          }

          canvases.push(canvas);

          return frameCallback(null);
        }
      );
    });
  }
}

function zeropad(str, len) {
  str = str.toString();

  while (str.length < len) {
    str = "0" + str;
  }

  return str;
}

module.exports = drawFrames;