PhantomJS: Capturing single dom elements as png files

gistfile1.js

var page = new WebPage(),
    address, output, size;



//capture and captureSelector functions adapted from CasperJS - https://github.com/n1k0/casperjs    
capture = function(targetFile, clipRect) {
    var previousClipRect;
    if (clipRect) {
        if (typeof(clipRect) !== "object") {
            throw new Error("clipRect must be an Object instance.");
        }
        page.clipRect = clipRect;
        console.log('Capturing page to ' + targetFile + ' with clipRect' + JSON.stringify(clipRect), "debug");
    } else {
        console.log('Capturing page to ' + targetFile, "debug");
    }
    try {
        page.render('buttonfactory/icons/' + targetFile);
    } catch (e) {
        console.log('Failed to capture screenshot as ' + targetFile + ': ' + e, "error");
    }
    if (previousClipRect) {
        page.clipRect = previousClipRect;
    }
    return this;
}

evaluate = function(fn, context) {
    context = (typeof(context) !== "object" ? context : {});
    var newFn = new functionInjector(fn).process(context);
    return page.evaluate(newFn);
},

        /**
* Captures the page area containing the provided selector.
*
* @param String targetFile Target destination file path.
* @param String selector CSS3 selector
* @return Casper
*/
captureSelector = function(targetFile, selector) {
    page.currentSelector = selector;
    var captureFunc = 'function(){return document.querySelector("'+selector+'").getBoundingClientRect()}';
    var cropBox = page.evaluate(captureFunc);
    return capture(targetFile, {top: cropBox.top, left: cropBox.left, width: cropBox.width, height: cropBox.height});
}

if (phantom.args.length != 1) {
    console.log('Usage: maketheme.js theme.html');
    phantom.exit();
} else {
    address = phantom.args[0];
    page.viewportSize = { width: 200, height: 200 };
    page.paperSize = { width: 1024, height: 768, border: '0px' }
    page.open(address, function (status) {
        if (status !== 'success') {
            console.log('Unable to load the address!');
        } else 
        {
            var iconRules = ['.ig-icon-alert','.ig-icon-arrow-1-n','.ig-icon-arrow-1-se','.long-gradient','.long-blue-gradient','.ig-icon-camera'];
            for (var i = 0; i < iconRules.length; i++){
               var iconSel = iconRules[i];
               captureSelector(iconSel.slice(1)+'.png',iconSel);
            }
            phantom.exit();
      }
    });
}