I use a bookmarklet that zoom or shrink images on a page.

	function zoomImage(image, amt)
	{
		if (image.initialHeight == null)
		{ /* avoid losing height due to integer rounding while zooming out */
			image.initialHeight = image.height;
			image.initialWidth = image.width;
			image.scalingFactor = 1;
		}
		image.scalingFactor *= amt;
		image.width = image.scalingFactor * image.initialWidth;
		image.height = image.scalingFactor * image.initialHeight;
	}
	for (i=0; i<document.images.length; ++i) { zoomImage(document.images[i], .5); }

This bookmarklet uses document.images which only exists for HTML documents and not XML documents. Using these bookmarklets on a page sent with an XML Content-Type such as application/xhtml+xml just gets you an error in Phoenix's Javascript Console that says document.images has no properties. So I set out to rewrite the bookmarklet using the proper W3C DOM.

function zoom(dir)
{
	switch(dir)
	{
		case "in":
			amt = 2;
			break;
		case "out":
			amt = .5;
			break;
		default:
			amt = 1;
	}
	var imgNodeList = document.getElementsByTagName('img');
	for (var i=0; i<imgNodeList.length; i++)
	{
		x = imgNodeList[i].width;
		x *= amt;

 		imgNodeList[i].setAttribute('width',x);
		y = imgNodeList[i].height;
		y *= amt;
		imgNodeList[i].setAttribute('height',y);
	}
}

I just use a switch because I never never used one before in JavaScript and wanted to try it out. My first instinct was to use a regular if.

I haven't checked to see if this works on a page where an IMG element does not have WIDTH and HEIGHT attributes already set. Also, I think I would prefer to set the CSS width and height properties instead of the HTML attributes.

You can see this code in action at The_Terror_of_Tim_Boo_Ba.html.