Color helper classes.
	
	Generate SVG filters that can be used to apply color overlays 
	to images in a web page via CSS.
	
	@author Charles Schoenfeld

	STEP 1:
	To write an SVG filter definition into your HTML, do the following. 

		<?php
		use CSchoenfeld\ColorSpec;
		use CSchoenfeld\Colorizer;
		try {
			/*
				In this example, you're trying to apply a 60% tint of orange 
				to some of the images in your page.
			*/
			$filterName = 'colorizeOrange';
			$colorOrange = new CSchoenfeld\ColorSpec();
			$colorOrange->setHex('f16234');
			$colorStrength = 60;
			$orangeFilter = CSchoenfeld\Colorizer::makeFilter($filterName, $colorOrange, $colorStrength);
			echo $orangeFilter;
		} catch (Exception $ex) {
			// Handle any exceptions here.
		}
		?>
	
	STEP 2:
	Reference this filter in your CSS, for browsers that support it.
	
		.orangeImage {
			filter: url(#colorizeOrange);
			-webkit-filter: url(#colorizeOrange);
		}
	
	And apply that CSS class to the image in your HTML.
	
		<img src="myimage.png" class="orangeImage" alt="orange image">