determineFontHeightInPixels -- proposed fix for Pixi.js

determineFontHeightInPixels.js

/*
 * http://stackoverflow.com/posts/13730758/revisions
 *
 * @method determineFontHeightInPixels
 * @param fontStyle {String}
 * @private
 */
PIXI.Text.prototype.determineFontHeightInPixels = function(fontStyle)
{
  var result = PIXI.Text.heightCache[fontStyle];

  if (!result) 
  {
    var fontDraw = document.createElement("canvas");
    var ctx = fontDraw.getContext('2d');
    ctx.fillRect(0, 0, fontDraw.width, fontDraw.height);
    ctx.textBaseline = 'top';
    ctx.fillStyle = 'white';
    ctx.font = fontStyle;
    ctx.fillText('gM', 0, 0);
    var pixels = ctx.getImageData(0, 0, fontDraw.width, fontDraw.height).data;
    var start = -1;
    var end = -1;
    for (var row = 0; row < fontDraw.height; row++) 
    {
      for (var column = 0; column < fontDraw.width; column++) 
      {
        var index = (row * fontDraw.width + column) * 4;
        if (pixels[index] === 0) {
          if (column === fontDraw.width - 1 && start !== -1) {
            end = row;
            row = fontDraw.height;
            break;
          }
          continue;
        }
        else 
        {
          if (start === -1) 
          {
            start = row;
          }
          break;
        }
      }
    }
    result = end - start;
    PIXI.Text.heightCache[fontStyle] = result;
  }
  return result;
};