Grayscale via CSS

http://thenewcode.com/532/Convert-Images-To-Black-And-White-With-CSS

tl;dr:

img.desaturate{
	-webkit-filter: grayscale(1);
	-webkit-filter: grayscale(100%);
	filter: gray;
	filter: grayscale(100%);
	filter: url(desaturate.svg#greyscale);
}

And the SVG File:

<svg version="1.1" xmlns="http://www.w3.org/2000/svg">
	<filter id="greyscale">
	<feColorMatrix type="matrix" values="0.3333 0.3333 0.3333 0 0
		0.3333 0.3333 0.3333 0 0
		0.3333 0.3333 0.3333 0 0
		0 0 0 1 0" />
	</filter>
</svg>

Or, inline the SVG and do it all in one place:

img.desaturate {
	-webkit-filter: grayscale(100%);
	filter: grayscale(100%);
	filter: gray;
	filter: url("data:image/svg+xml;utf8,<svg version='1.1' xmlns='http://www.w3.org/2000/svg' height='0'><filter id='greyscale'><feColorMatrix type='matrix' values='0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0 0 0 1 0' /></filter></svg>#greyscale");
}