Javascript Image Utils

TSImageUtils.js

function TSCenterImage(img)
	{
	if (!img || !img.offsetParent) return;

	// get the basic metrics
	var iw = img.naturalWidth, ih = img.naturalHeight, ww = img.offsetParent.offsetWidth, wh = img.offsetParent.offsetHeight;
	if (!iw || !ih || !ww || !wh) return;

	// calculate the scale by fitting image to align container's width and height
	var sw = ww/iw, sh = wh/ih;

	// calculate scaled image width / height under the above scales
	var sih = ih * sw, siw = iw * sh;

	var x=0, y=0, w=ww, h=wh;
	if (sih < wh)
		{
		// if scaled image height fits inside the container:
		h = sih;
		y = (wh - h)/2;
		}
	else
		{
		// if scaled image width fits inside the container:
		w = siw;
		x = (ww - w) / 2;
		}

	img.style.left = x + 'px';
	img.style.top = y + 'px';
	img.style.width = w + 'px';
	img.style.height = h + 'px';
	}