_html2canvas.Util.Font = (function () {

var fontData = {};

return function(font, fontSize, doc) {

if (fontData[font + "-" + fontSize] !== undefined) {

return fontData[font + "-" + fontSize];

}

var container = doc.createElement('div'),

img = doc.createElement('img'),

span = doc.createElement('span'),

sampleText = 'Hidden Text',

baseline,

middle,

metricsObj;

container.style.visibility = "hidden";

container.style.fontFamily = font;

container.style.fontSize = fontSize;

container.style.margin = 0;

container.style.padding = 0;

doc.body.appendChild(container);

// http://probablyprogramming.com/2009/03/15/the-tiniest-gif-ever (handtinywhite.gif)

img.src = "data:image/gif;base64,R0lGODlhAQABAIABAP///wAAACwAAAAAAQABAAACAkQBADs=";

img.width = 1;

img.height = 1;

img.style.margin = 0;

img.style.padding = 0;

img.style.verticalAlign = "baseline";

span.style.fontFamily = font;

span.style.fontSize = fontSize;

span.style.margin = 0;

span.style.padding = 0;

span.appendChild(doc.createTextNode(sampleText));

container.appendChild(span);

container.appendChild(img);

baseline = (img.offsetTop - span.offsetTop) + 1;

container.removeChild(span);

container.appendChild(doc.createTextNode(sampleText));

container.style.lineHeight = "normal";

img.style.verticalAlign = "super";

middle = (img.offsetTop-container.offsetTop) + 1;

metricsObj = {

baseline: baseline,

lineWidth: 1,

middle: middle

};

fontData[font + "-" + fontSize] = metricsObj;

doc.body.removeChild(container);

return metricsObj;

};

})();