PhantomJS: Capturing single dom elements as png files

Create Screenshot of supplied CSS selector

var page = new WebPage(),
    address, output, size;
 var retval = {};  
retval.result = "failed";
retval.messages = [];

//capture and captureSelector functions adapted from CasperJS - https://github.com/n1k0/casperjs
capture = function(targetFile, clipRect) {

    try {
        page.render(targetFile);
    } catch (e) {
    	return false;
	}
    return this;
}

captureSelector = function(targetFile, selector) {
    var selector = selector;
    return capture(targetFile, page.evaluate(function(selector) {  
        try { 
            var clipRect = document.querySelector(selector).getBoundingClientRect();
            return {
                top: clipRect.top,
                left: clipRect.left,
                width: clipRect.width,
                height: clipRect.height
            };
        } catch (e) {
        	
        }
    }, { selector: selector }));
}

if (phantom.args.length < 2) {
    //console.log('Usage: test2.js buttons.html .selector_class');
    retval.messages.push("2 arguments required.");
    console.log(JSON.stringify(retval,undefined,4));
    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 
        {
        	console.log(phantom.args[1]);
           //dump out each icon in buttons.html as individual png file
           var outputfile = Math.round(Math.random() * 1000000) + ".png";
           if(captureSelector("/Users/rrrhys/projects/invites_ci/invitations/" + outputfile,phantom.args[1])){
           	
           	retval['result'] = "success";
           	retval['filename'] = outputfile;
            console.log(JSON.stringify(retval,undefined,4));
           }
           else{
	       
	   	} 
            phantom.exit();
      }
    });
}