(function($) {
		var has_VML, create_canvas_for, add_shape_to, clear_canvas, shape_from_area,
			canvas_style, hex_to_decimal, css3color, is_image_loaded, options_from_area;
	
		has_VML = document.namespaces;
		has_canvas = !!document.createElement('canvas').getContext;
	
		if(!(has_canvas || has_VML)) {
			$.fn.maphilight = function() { return this; };
			return;
		}
		
		if(has_canvas) {
			hex_to_decimal = function(hex) {
				return Math.max(0, Math.min(parseInt(hex, 16), 255));
			};
			css3color = function(color, opacity) {
				return 'rgba('+hex_to_decimal(color.substr(0,2))+','+hex_to_decimal(color.substr(2,2))+','+hex_to_decimal(color.substr(4,2))+','+opacity+')';
			};
			create_canvas_for = function(img) {
				var c = $('<canvas style="width:'+img.width+'px;height:'+img.height+'px;"></canvas>').get(0);
				c.getContext("2d").clearRect(0, 0, c.width, c.height);
				return c;
			};
			add_shape_to = function(canvas, shape, coords, options, name) {
				var i, context = canvas.getContext('2d');
				context.beginPath();
				if(shape == 'rect') {
					context.rect(coords[0], coords[1], coords[2] - coords[0], coords[3] - coords[1]);
				} else if(shape == 'poly') {
					context.moveTo(coords[0], coords[1]);
					for(i=2; i < coords.length; i+=2) {
						context.lineTo(coords[i], coords[i+1]);
					}
				} else if(shape == 'circ') {
					context.arc(coords[0], coords[1], coords[2], 0, Math.PI * 2, false);
				}
				context.closePath();
				if(options.fill) {
					context.fillStyle = css3color(options.fillColor, options.fillOpacity);
					context.fill();
				}
				if(options.stroke) {
					context.strokeStyle = css3color(options.strokeColor, options.strokeOpacity);
					context.lineWidth = options.strokeWidth;
					context.stroke();
				}
				if(options.fade) {
					$(canvas).css('opacity', 0).animate({opacity: 1}, 100);
				}
			};
			clear_canvas = function(canvas) {
				canvas.getContext('2d').clearRect(0, 0, canvas.width,canvas.height);
			};
		} else {   // ie executes this code
			create_canvas_for = function(img) {
				return $('<var style="zoom:1;overflow:hidden;display:block;width:'+img.width+'px;height:'+img.height+'px;"></var>').get(0);
			};
			add_shape_to = function(canvas, shape, coords, options, name) {
				var fill, stroke, opacity, e;
				fill = '<v:fill color="#'+options.fillColor+'" opacity="'+(options.fill ? options.fillOpacity : 0)+'" />';
				stroke = (options.stroke ? 'strokeweight="'+options.strokeWidth+'" stroked="t" strokecolor="#'+options.strokeColor+'"' : 'stroked="f"');
				opacity = '<v:stroke opacity="'+options.strokeOpacity+'"/>';
				if(shape == 'rect') {
					e = $('<v:rect name="'+name+'" filled="t" '+stroke+' style="zoom:1;margin:0;padding:0;display:block;position:absolute;left:'+coords[0]+'px;top:'+coords[1]+'px;width:'+(coords[2] - coords[0])+'px;height:'+(coords[3] - coords[1])+'px;"></v:rect>');
				} else if(shape == 'poly') {
					e = $('<v:shape name="'+name+'" filled="t" '+stroke+' coordorigin="0,0" coordsize="'+canvas.width+','+canvas.height+'" path="m '+coords[0]+','+coords[1]+' l '+coords.join(',')+' x e" style="zoom:1;margin:0;padding:0;display:block;position:absolute;top:0px;left:0px;width:'+canvas.width+'px;height:'+canvas.height+'px;"></v:shape>');
				} else if(shape == 'circ') {
					e = $('<v:oval name="'+name+'" filled="t" '+stroke+' style="zoom:1;margin:0;padding:0;display:block;position:absolute;left:'+(coords[0] - coords[2])+'px;top:'+(coords[1] - coords[2])+'px;width:'+(coords[2]*2)+'px;height:'+(coords[2]*2)+'px;"></v:oval>');
				}
				e.get(0).innerHTML = fill+opacity;
				$(canvas).append(e);
			};
			clear_canvas = function(canvas) {
				$(canvas).find('[name=highlighted]').remove();
			};
		}
		
		shape_from_area = function(area) {
			var i, coords = area.getAttribute('coords').split(',');
			for (i=0; i < coords.length; i++) { coords[i] = parseFloat(coords[i]); }
			return [area.getAttribute('shape').toLowerCase().substr(0,4), coords];
		};
	
		options_from_area = function(area, options) {
			var $area = $(area);
			return $.extend({}, options, $.metadata ? $area.metadata() : false, $area.data('maphilight'));
		};
		
		is_image_loaded = function(img) {
			if(!img.complete) { return false; } // IE
			if(typeof img.naturalWidth != "undefined" && img.naturalWidth == 0) { return false; } // Others
			return true;
		};
	
		canvas_style = {
			position: 'absolute',
			left: 0,
			top: 0,
			padding: 0,
			border: 0
		};
		
		var ie_hax_done = false;
		$.fn.maphilight = function(opts) {
			opts = $.extend({}, $.fn.maphilight.defaults, opts);
			
			if(!has_canvas && $.browser.msie && !ie_hax_done) {
				document.namespaces.add("v", "urn:schemas-microsoft-com:vml");
				var style = document.createStyleSheet();
				var shapes = ['shape','rect', 'oval', 'circ', 'fill', 'stroke', 'imagedata', 'group','textbox'];
				$.each(shapes,
					function() {
						style.addRule('v\\:' + this, "behavior: url(#default#VML); antialias:true");
					}
				);
				ie_hax_done = true;
			}
			
			return this.each(function() {
				var img, wrap, options, map, canvas, canvas_always, mouseover, highlighted_shape, usemap;
				img = $(this);
	
				if(!is_image_loaded(this)) {
					// If the image isn't fully loaded, this won't work right.  Try again later.
					return window.setTimeout(function() {
						img.maphilight(opts);
					}, 200);
				}
	
				options = $.extend({}, opts, $.metadata ? img.metadata() : false, img.data('maphilight'));
	
				// jQuery bug with Opera, results in full-url#usemap being returned from jQuery's attr.
				// So use raw getAttribute instead.
				usemap = img.get(0).getAttribute('usemap');
	
				map = $('map[name="'+usemap.substr(1)+'"]');
	
				if(!(img.is('img') && usemap && map.size() > 0)) {
					return;
				}
	
				if(img.hasClass('maphilighted')) {
					// We're redrawing an old map, probably to pick up changes to the options.
					// Just clear out all the old stuff.
					var wrapper = img.parent();
					img.insertBefore(wrapper);
					wrapper.remove();
					$(map).unbind('.maphilight').find('area[coords]').unbind('.maphilight');
				}
	
				wrap = $('<div></div>').css({
					display:'block',
					background:'url("'+this.src+'")',
					position:'relative',
					padding:0,
					width:this.width,
					height:this.height
					});
				if(options.wrapClass) {
					if(options.wrapClass === true) {
						wrap.addClass($(this).attr('class'));
					} else {
						wrap.addClass(options.wrapClass);
					}
				}
				img.before(wrap).css('opacity', 0).css(canvas_style).remove();
				if($.browser.msie) { img.css('filter', 'Alpha(opacity=0)'); }
				wrap.append(img);
				
				canvas = create_canvas_for(this);
				$(canvas).css(canvas_style);
				canvas.height = this.height;
				canvas.width = this.width;
				
				mouseover = function(e) {
					var shape, area_options;
					area_options = options_from_area(this, options);
					if(
						!area_options.neverOn
						&&
						!area_options.alwaysOn
					) {
						shape = shape_from_area(this);
						add_shape_to(canvas, shape[0], shape[1], area_options, "highlighted");
						if(area_options.groupBy) {
							var areas;
							// two ways groupBy might work; attribute and selector
							if(/^[a-zA-Z][-a-zA-Z]+$/.test(area_options.groupBy)) {
								areas = map.find('area['+area_options.groupBy+'="'+$(this).attr(area_options.groupBy)+'"]')
							} else {
								areas = map.find(area_options.groupBy);
							}
							var first = this;
							areas.each(function() {
								if(this != first) {
									var subarea_options = options_from_area(this, options);
									if(!subarea_options.neverOn && !subarea_options.alwaysOn) {
										var shape = shape_from_area(this);
										add_shape_to(canvas, shape[0], shape[1], subarea_options, "highlighted");
									}
								}
							});
						}
						// workaround for IE7, IE8 not rendering the final rectangle in a group
						if(!has_canvas) {
							$(canvas).append('<v:rect></v:rect>');
						}
					}
				}
	
				$(map).bind('alwaysOn.maphilight', function() {
					// Check for areas with alwaysOn set. These are added to a *second* canvas,
					// which will get around flickering during fading.
					if(canvas_always) {
						clear_canvas(canvas_always)
					}
					if(!has_canvas) {
						$(canvas).empty();
					}
					$(map).find('area[coords]').each(function() {
						var shape, area_options;
						area_options = options_from_area(this, options);
						if(area_options.alwaysOn) {
							if(!canvas_always && has_canvas) {
								canvas_always = create_canvas_for(img.get());
								$(canvas_always).css(canvas_style);
								canvas_always.width = img.width();
								canvas_always.height = img.height();
								img.before(canvas_always);
							}
							area_options.fade = area_options.alwaysOnFade; // alwaysOn shouldn't fade in initially
							shape = shape_from_area(this);
							if (has_canvas) {
								add_shape_to(canvas_always, shape[0], shape[1], area_options, "");
							} else {
								add_shape_to(canvas, shape[0], shape[1], area_options, "");
							}
						}
					});
				});
				
				$(map).trigger('alwaysOn.maphilight').find('area[coords]')
					.bind('mouseover.maphilight', mouseover)
					.bind('mouseout.maphilight', function(e) { clear_canvas(canvas); });;
				
				img.before(canvas); // if we put this after, the mouseover events wouldn't fire.
				
				img.addClass('maphilighted');
			});
		};
		$.fn.maphilight.defaults = {
			fill: true,
			fillColor: '000000',
			fillOpacity: 0.2,
			stroke: true,
			strokeColor: 'ff0000',
			strokeOpacity: 1,
			strokeWidth: 1,
			fade: true,
			alwaysOn: false,
			neverOn: false,
			groupBy: false,
			wrapClass: true
		};
	})(jQuery);