Improved PhantomJS rasterize script

rasterize.js

//  Takes a screenshot of a URL or HTML string. Optionally, set viewport size
//  and resolution, or capture only a specific element
//
//  Usage: `phantomjs rasterize.js URL|[or URI encoded HTML string] output size scale element`
//
//  Examples:
//    `phantomjs rasterize.js http://google.com google.png`
//    `phantomjs rasterize.js http://google.com img/google-logo.png auto 1 \#hplogo`
//    `phantomjs rasterize.js %3Chtml%3E%3Cbody%3E%3Ch1%3EHello%20world!%3C%2Fh1%3E%3C%2Fbody%3E%3C%2Fhtml%3E hello-world.png
//
//  Arguments:
//    URL or HTML: A URL or a URI encoded string of HTML
//    output:      The path and filename of the screenshot
//    size:        The nominal size of the viewport.
//                 If `scale` is passed, `size` will be multiplied by `scale`.
//                 This argument is ignored if `element` is passed.
//    scale:       The scaling factor.
//                 Use to simulate high-res, retina viewports.
//    element:     A specific DOM selector to capture.
//                 Clips the screenshot to the element.
//                 On the command line, be sure to escape ID selectors (`#id`)
//                 with a backslash (`\`), i.e.: `\#id`

/* globals require, phantom */

var page = require('webpage').create(),
    system = require('system'),
    args = system.args,
    urlOrHTML, outputFile, size, scale, element, preflight, pageWidth, pageHeight;

preflight = function() {
  var clipDimensions;

  if (scale) {
    page.evaluate(function(scale) {
      document.body.style.webkitTransform = "scale(" + scale + ")";
      document.body.style.webkitTransformOrigin = "0% 0%";
      document.body.style.width = (100 / scale) + "%";
      return;
    }, scale);
  }

  if (element) {
    clipDimensions = page.evaluate(function(element) {
      element = document.querySelector(element);

      if (! element) {
        console.log('Unable to load ' + element + ', exiting');
        return false;
      }

      return element.getBoundingClientRect();
    }, element);

    page.clipRect = clipDimensions;
  }
};

if (args.length < 3 || args.length > 6) {
  console.log('Usage: rasterize.js URL|HTML output size scale element');
  console.log('  size examples: "1920px", "800px*600px", "auto"');
  phantom.exit(1);
}

else {
  urlOrHTML = decodeURIComponent(args[1]);
  outputFile = args[2];
  size = args[3] !== null ? args[3].split('*') : [];
  scale = args[4];
  element = args[5];

  page.viewportSize = { width: 800, height: 600 };

  if (size && size != 'auto') {
    // Width and height dimensions were passed in with X*Y format
    if (size.length === 2) {
      pageWidth = parseInt(size[0], 10);
      pageHeight = parseInt(size[1], 10);
      page.viewportSize = { width: pageWidth, height: pageHeight };
      page.clipRect = { top: 0, left: 0, width: pageWidth, height: pageHeight };
    }

    // Only width was passed
    else {
      pageWidth = parseInt(size, 10);
      pageHeight = parseInt(pageWidth * 3/4, 10); // it's as good an assumption as any
      page.viewportSize = { width: pageWidth, height: pageHeight };
    }
  }

  if (scale) {
    page.viewportSize = {
      width: page.viewportSize.width * scale,
      height: page.viewportSize.height * scale
    };
  }

  if (urlOrHTML.match('http')) {
    page.open(urlOrHTML, function(status) {
      if (status !== 'success') {
        console.log('Unable to load the URL!');
        phantom.exit(1);
      }

      else {
        window.setTimeout(function() {
          preflight();
          page.render(outputFile);
          phantom.exit();
        }, 200);
      }
    });
  }

  else {
    page.setContent(urlOrHTML, null);
    preflight();
    page.render(outputFile);
    phantom.exit();
  }
}