message: Add high dpr support in node or other environment with only one canvas
diff: @@ -175,21 +175,27 @@ var Painter = function (root, storage, opts) {
  root.appendChild(domRoot);
  }
  else {
  + var width = root.width;
  + var height = root.height;
  +
  if (opts.width != null) {
  - root.width = opts.width;
  + width = opts.width;
  }
  if (opts.height != null) {
  - root.height = opts.height;
  + height = opts.height;
  }
  + this.dpr = opts.devicePixelRatio || 1;
  +
  // Use canvas width and height directly
  - var width = root.width;
  - var height = root.height;
  + root.width = width * this.dpr;
  + root.height = height * this.dpr;
  +
  this._width = width;
  this._height = height;
  // Create layer if only one given canvas
  - // Device pixel ratio is fixed to 1 because given canvas has its specified width and height
  - var mainLayer = new Layer(root, this, 1);
  + // Device can be specified to create a high dpi image.
  + var mainLayer = new Layer(root, this, this.dpr);
  mainLayer.__builtin__ = true;
  mainLayer.initContext();
  // FIXME Use canvas width and height
  