Overview

  This script accepts a sprite file as input and outputs the proper css rules for a selection image
	or portion of the sprite file. Two features of note are:

	- It uses the new files API from HTML5 to read files from a browser PC's local drive
	- It utilizes the Canvas object from CSS3 to manipulate the sprite image

	The image file must first be selected from the local drive. Go to the Input tab and
	click the button to browse and choose the file. The sprite file will be displayed
	to the right.

	Default operation is to click on an image on the sprite. You'll see a rectangle with a blue border
	grow around the 	selected area. If you wish to expand or reduce the selected area simply click
	on the sprite outside the presently selected area to cause the border to reappear, then click and
	drag to manually select the desired area. This is useful for selecting text and other non-contiguous
	images.

	You can instead click and drag around an image you'd like to select. This is helpful when you wish
	to select text, or multiple objects. If adjustments to the rectangle size, use the mouse along the
	inner edges of the rectangle or update the pixel settings on the Input tab to grow or shrink the
	selection.

	Go to the Output tab to copy the generated CSS of the clipped image to your HTML or CSS file.