zoomFactor
zoomFactor {number}
This property specifies the scaling factor for the page.render and page.renderBase64 functions.
The default is 1, i.e. 100% zoom.
Examples
Create a thumbnail preview with 25% zoom
var webPage = require('webpage');
var page = webPage.create();
page.zoomFactor = 0.25;
page.render('capture.png');