IE6透明PNG解决方案

IE6不支持PNG-24图片一直困扰很多人，但是可以通过IE的独有的滤镜来解决，解决的方案很多，比如：将滤镜写在CSS里，还可以写成单独的Javascript文件，本来认为推荐两种做法：第一种，将所有PNG图片添加滤镜（此方法有副作用）；第二种：有选择性的添加滤镜（推荐）；两者都可以将代码放在单独的JS文件里，然后引用。

 

第一种：

直接添加如下代码：

 

 

function correctPNG() {
	for (var i = 0; i < document.images.length; i++) {
		var img = document.images[i];
		var imgName = img.src.toUpperCase();
		if (imgName.substring(imgName.length - 3, imgName.length) == "PNG") {
			var imgID = (img.id) ? "id='" + img.id + "' " : "";
			var imgClass = (img.className) ? "class='" + img.className + "' " : "";
			var imgTitle = (img.title) ? "title='" + img.title + "' " : "title='" + img.alt + "' ";
			var imgStyle = "display:inline-block;" + img.style.cssText;
			if (img.align == "left") {
				imgStyle = "float:left;" + imgStyle;
			}
			if (img.align == "right") {
				imgStyle = "float:right;" + imgStyle;
			}
			if (img.parentElement.href) {
				imgStyle = "cursor:hand;" + imgStyle;
			}
			var strNewHTML = "<span " + imgID + imgClass + imgTitle + " style=\"" + "width:" + img.width + "px; height:" + img.height + "px;" + imgStyle + ";" + "filter:progid:DXImageTransform.Microsoft.AlphaImageLoader" + "(src=\'" + img.src + "\', sizingMethod='scale');\"></span>";
			img.outerHTML = strNewHTML;
			i = i - 1;
		}
	}
}
function alphaBackgrounds() {
	var rslt = navigator.appVersion.match(/MSIE(d+.d+)/, '');
	var itsAllGood = (rslt !== null && Number(rslt[1]) >= 5.5);
	for (i = 0; i < document.all.length; i++) {
		var bg = document.all[i].currentStyle.backgroundImage;
		if (bg) {
			if (bg.match(/.png/i) !== null) {
				var mypng = bg.substring(5, bg.length - 2);
				document.all[i].style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(src ='" +
					mypng + "',sizingMethod='crop')";
				document.all[i].style.backgroundImage = "url('')";
			}
		}
	}
}
if (navigator.userAgent.indexOf("MSIE 6.0") > -1) {
	window.attachEvent("onload", correctPNG);
	window.attachEvent("onload", alphaBackgrounds);
}

 

 

 

第二种：

1）添加以下代码：

 

 

var DD_belatedPNG = {
	ns: 'DD_belatedPNG',
	imgSize: {},
	delay: 10,
	nodesFixed: 0,
	createVmlNameSpace: function () { /* enable VML */
		if (document.namespaces && !document.namespaces[this.ns]) {
			document.namespaces.add(this.ns, 'urn:schemas-microsoft-com:vml');
		}
	},
	createVmlStyleSheet: function () { /* style VML, enable behaviors */
		/*
			Just in case lots of other developers have added
			lots of other stylesheets using document.createStyleSheet
			and hit the 31-limit mark, let's not use that method!
			further reading: http://msdn.microsoft.com/en-us/library/ms531194(VS.85).aspx
		*/
		var screenStyleSheet, printStyleSheet;
		screenStyleSheet = document.createElement('style');
		screenStyleSheet.setAttribute('media', 'screen');
		document.documentElement.firstChild.insertBefore(screenStyleSheet, document.documentElement.firstChild.firstChild);
		if (screenStyleSheet.styleSheet) {
			screenStyleSheet = screenStyleSheet.styleSheet;
			screenStyleSheet.addRule(this.ns + '\\:*', '{behavior:url(#default#VML)}');
			screenStyleSheet.addRule(this.ns + '\\:shape', 'position:absolute;');
			screenStyleSheet.addRule('img.' + this.ns + '_sizeFinder', 'behavior:none; border:none; position:absolute; z-index:-1; top:-10000px; visibility:hidden;'); /* large negative top value for avoiding vertical scrollbars for large images, suggested by James O'Brien, http://www.thanatopsic.org/hendrik/ */
			this.screenStyleSheet = screenStyleSheet;
			
			/* Add a print-media stylesheet, for preventing VML artifacts from showing up in print (including preview). */
			/* Thanks to R閙i Pr関ost for automating this! */
			printStyleSheet = document.createElement('style');
			printStyleSheet.setAttribute('media', 'print');
			document.documentElement.firstChild.insertBefore(printStyleSheet, document.documentElement.firstChild.firstChild);
			printStyleSheet = printStyleSheet.styleSheet;
			printStyleSheet.addRule(this.ns + '\\:*', '{display: none !important;}');
			printStyleSheet.addRule('img.' + this.ns + '_sizeFinder', '{display: none !important;}');
		}
	},
	readPropertyChange: function () {
		var el, display, v;
		el = event.srcElement;
		if (!el.vmlInitiated) {
			return;
		}
		if (event.propertyName.search('background') != -1 || event.propertyName.search('border') != -1) {
			DD_belatedPNG.applyVML(el);
		}
		if (event.propertyName == 'style.display') {
			display = (el.currentStyle.display == 'none') ? 'none' : 'block';
			for (v in el.vml) {
				if (el.vml.hasOwnProperty(v)) {
					el.vml[v].shape.style.display = display;
				}
			}
		}
		if (event.propertyName.search('filter') != -1) {
			DD_belatedPNG.vmlOpacity(el);
		}
	},
	vmlOpacity: function (el) {
		if (el.currentStyle.filter.search('lpha') != -1) {
			var trans = el.currentStyle.filter;
			trans = parseInt(trans.substring(trans.lastIndexOf('=')+1, trans.lastIndexOf(')')), 10)/100;
			el.vml.color.shape.style.filter = el.currentStyle.filter; /* complete guesswork */
			el.vml.image.fill.opacity = trans; /* complete guesswork */
		}
	},
	handlePseudoHover: function (el) {
		setTimeout(function () { /* wouldn't work as intended without setTimeout */
			DD_belatedPNG.applyVML(el);
		}, 1);
	},
	/**
	* This is the method to use in a document.
	* @param {String} selector - REQUIRED - a CSS selector, such as '#doc .container'
	**/
	fix: function (selector) {
		if (this.screenStyleSheet) {
			var selectors, i;
			selectors = selector.split(','); /* multiple selectors supported, no need for multiple calls to this anymore */
			for (i=0; i<selectors.length; i++) {
				this.screenStyleSheet.addRule(selectors[i], 'behavior:expression(DD_belatedPNG.fixPng(this))'); /* seems to execute the function without adding it to the stylesheet - interesting... */
			}
		}
	},
	applyVML: function (el) {
		el.runtimeStyle.cssText = '';
		this.vmlFill(el);
		this.vmlOffsets(el);
		this.vmlOpacity(el);
		if (el.isImg) {
			this.copyImageBorders(el);
		}
	},
	attachHandlers: function (el) {
		var self, handlers, handler, moreForAs, a, h;
		self = this;
		handlers = {resize: 'vmlOffsets', move: 'vmlOffsets'};
		if (el.nodeName == 'A') {
			moreForAs = {mouseleave: 'handlePseudoHover', mouseenter: 'handlePseudoHover', focus: 'handlePseudoHover', blur: 'handlePseudoHover'};
			for (a in moreForAs) {			
				if (moreForAs.hasOwnProperty(a)) {
					handlers[a] = moreForAs[a];
				}
			}
		}
		for (h in handlers) {
			if (handlers.hasOwnProperty(h)) {
				handler = function () {
					self[handlers[h]](el);
				};
				el.attachEvent('on' + h, handler);
			}
		}
		el.attachEvent('onpropertychange', this.readPropertyChange);
	},
	giveLayout: function (el) {
		el.style.zoom = 1;
		if (el.currentStyle.position == 'static') {
			el.style.position = 'relative';
		}
	},
	copyImageBorders: function (el) {
		var styles, s;
		styles = {'borderStyle':true, 'borderWidth':true, 'borderColor':true};
		for (s in styles) {
			if (styles.hasOwnProperty(s)) {
				el.vml.color.shape.style[s] = el.currentStyle[s];
			}
		}
	},
	vmlFill: function (el) {
		if (!el.currentStyle) {
			return;
		} else {
			var elStyle, noImg, lib, v, img, imgLoaded;
			elStyle = el.currentStyle;
		}
		for (v in el.vml) {
			if (el.vml.hasOwnProperty(v)) {
				el.vml[v].shape.style.zIndex = elStyle.zIndex;
			}
		}
		el.runtimeStyle.backgroundColor = '';
		el.runtimeStyle.backgroundImage = '';
		noImg = true;
		if (elStyle.backgroundImage != 'none' || el.isImg) {
			if (!el.isImg) {
				el.vmlBg = elStyle.backgroundImage;
				el.vmlBg = el.vmlBg.substr(5, el.vmlBg.lastIndexOf('")')-5);
			}
			else {
				el.vmlBg = el.src;
			}
			lib = this;
			if (!lib.imgSize[el.vmlBg]) { /* determine size of loaded image */
				img = document.createElement('img');
				lib.imgSize[el.vmlBg] = img;
				img.className = lib.ns + '_sizeFinder';
				img.runtimeStyle.cssText = 'behavior:none; position:absolute; left:-10000px; top:-10000px; border:none; margin:0; padding:0;'; /* make sure to set behavior to none to prevent accidental matching of the helper elements! */
				imgLoaded = function () {
					this.width = this.offsetWidth; /* weird cache-busting requirement! */
					this.height = this.offsetHeight;
					lib.vmlOffsets(el);
				};
				img.attachEvent('onload', imgLoaded);
				img.src = el.vmlBg;
				img.removeAttribute('width');
				img.removeAttribute('height');
				document.body.insertBefore(img, document.body.firstChild);
			}
			el.vml.image.fill.src = el.vmlBg;
			noImg = false;
		}
		el.vml.image.fill.on = !noImg;
		el.vml.image.fill.color = 'none';
		el.vml.color.shape.style.backgroundColor = elStyle.backgroundColor;
		el.runtimeStyle.backgroundImage = 'none';
		el.runtimeStyle.backgroundColor = 'transparent';
	},
	/* IE can't figure out what do when the offsetLeft and the clientLeft add up to 1, and the VML ends up getting fuzzy... so we have to push/enlarge things by 1 pixel and then clip off the excess */
	vmlOffsets: function (el) {
		var thisStyle, size, fudge, makeVisible, bg, bgR, dC, altC, b, c, v;
		thisStyle = el.currentStyle;
		size = {'W':el.clientWidth+1, 'H':el.clientHeight+1, 'w':this.imgSize[el.vmlBg].width, 'h':this.imgSize[el.vmlBg].height, 'L':el.offsetLeft, 'T':el.offsetTop, 'bLW':el.clientLeft, 'bTW':el.clientTop};
		fudge = (size.L + size.bLW == 1) ? 1 : 0;
		/* vml shape, left, top, width, height, origin */
		makeVisible = function (vml, l, t, w, h, o) {
			vml.coordsize = w+','+h;
			vml.coordorigin = o+','+o;
			vml.path = 'm0,0l'+w+',0l'+w+','+h+'l0,'+h+' xe';
			vml.style.width = w + 'px';
			vml.style.height = h + 'px';
			vml.style.left = l + 'px';
			vml.style.top = t + 'px';
		};
		makeVisible(el.vml.color.shape, (size.L + (el.isImg ? 0 : size.bLW)), (size.T + (el.isImg ? 0 : size.bTW)), (size.W-1), (size.H-1), 0);
		makeVisible(el.vml.image.shape, (size.L + size.bLW), (size.T + size.bTW), (size.W), (size.H), 1 );
		bg = {'X':0, 'Y':0};
		if (el.isImg) {
			bg.X = parseInt(thisStyle.paddingLeft, 10) + 1;
			bg.Y = parseInt(thisStyle.paddingTop, 10) + 1;
		}
		else {
			for (b in bg) {
				if (bg.hasOwnProperty(b)) {
					this.figurePercentage(bg, size, b, thisStyle['backgroundPosition'+b]);
				}
			}
		}
		el.vml.image.fill.position = (bg.X/size.W) + ',' + (bg.Y/size.H);
		bgR = thisStyle.backgroundRepeat;
		dC = {'T':1, 'R':size.W+fudge, 'B':size.H, 'L':1+fudge}; /* these are defaults for repeat of any kind */
		altC = { 'X': {'b1': 'L', 'b2': 'R', 'd': 'W'}, 'Y': {'b1': 'T', 'b2': 'B', 'd': 'H'} };
		if (bgR != 'repeat' || el.isImg) {
			c = {'T':(bg.Y), 'R':(bg.X+size.w), 'B':(bg.Y+size.h), 'L':(bg.X)}; /* these are defaults for no-repeat - clips down to the image location */
			if (bgR.search('repeat-') != -1) { /* now let's revert to dC for repeat-x or repeat-y */
				v = bgR.split('repeat-')[1].toUpperCase();
				c[altC[v].b1] = 1;
				c[altC[v].b2] = size[altC[v].d];
			}
			if (c.B > size.H) {
				c.B = size.H;
			}
			el.vml.image.shape.style.clip = 'rect('+c.T+'px '+(c.R+fudge)+'px '+c.B+'px '+(c.L+fudge)+'px)';
		}
		else {
			el.vml.image.shape.style.clip = 'rect('+dC.T+'px '+dC.R+'px '+dC.B+'px '+dC.L+'px)';
		}
	},
	figurePercentage: function (bg, size, axis, position) {
		var horizontal, fraction;
		fraction = true;
		horizontal = (axis == 'X');
		switch(position) {
			case 'left':
			case 'top':
				bg[axis] = 0;
				break;
			case 'center':
				bg[axis] = 0.5;
				break;
			case 'right':
			case 'bottom':
				bg[axis] = 1;
				break;
			default:
				if (position.search('%') != -1) {
					bg[axis] = parseInt(position, 10) / 100;
				}
				else {
					fraction = false;
				}
		}
		bg[axis] = Math.ceil(  fraction ? ( (size[horizontal?'W': 'H'] * bg[axis]) - (size[horizontal?'w': 'h'] * bg[axis]) ) : parseInt(position, 10)  );
		if (bg[axis] % 2 === 0) {
			bg[axis]++;
		}
		return bg[axis];
	},
	fixPng: function (el) {
		el.style.behavior = 'none';
		var lib, els, nodeStr, v, e;
		if (el.nodeName == 'BODY' || el.nodeName == 'TD' || el.nodeName == 'TR') { /* elements not supported yet */
			return;
		}
		el.isImg = false;
		if (el.nodeName == 'IMG') {
			if(el.src.toLowerCase().search(/\.png$/) != -1) {
				el.isImg = true;
				el.style.visibility = 'hidden';
			}
			else {
				return;
			}
		}
		else if (el.currentStyle.backgroundImage.toLowerCase().search('.png') == -1) {
			return;
		}
		lib = DD_belatedPNG;
		el.vml = {color: {}, image: {}};
		els = {shape: {}, fill: {}};
		for (v in el.vml) {
			if (el.vml.hasOwnProperty(v)) {
				for (e in els) {
					if (els.hasOwnProperty(e)) {
						nodeStr = lib.ns + ':' + e;
						el.vml[v][e] = document.createElement(nodeStr);
					}
				}
				el.vml[v].shape.stroked = false;
				el.vml[v].shape.appendChild(el.vml[v].fill);
				el.parentNode.insertBefore(el.vml[v].shape, el);
			}
		}
		el.vml.image.shape.fillcolor = 'none'; /* Don't show blank white shapeangle when waiting for image to load. */
		el.vml.image.fill.type = 'tile'; /* Makes image show up. */
		el.vml.color.fill.on = false; /* Actually going to apply vml element's style.backgroundColor, so hide the whiteness. */
		lib.attachHandlers(el);
		lib.giveLayout(el);
		lib.giveLayout(el.offsetParent);
		el.vmlInitiated = true;
		lib.applyVML(el); /* Render! */
	}
};
try {
	document.execCommand("BackgroundImageCache", false, true); /* TredoSoft Multiple IE doesn't like this, so try{} it */
} catch(r) {}
DD_belatedPNG.createVmlNameSpace();
DD_belatedPNG.createVmlStyleSheet();

 

 

2）第二步在调用：

 

<!--[if IE 6]>   
<script src="js/DD_belatedPNG.js" mce_src="DD_belatedPNG.js"></script>   
<script type="text/javascript">     
 DD_belatedPNG.fix('.class');//这里是CSS选择，多个就有分号“，”隔开；
 如：DD_belatedPNG.fix('.class1,.class2,.class3')
</script> 
<![endif]-->

 

 

 第二种方法使用得比较多，可以根据需要选择滤镜，不会影响其它图片，副作用小。

虽然可以使用滤镜来解决透明的问题，但是这也是有条件的，所使用的图片不能 background-position: 与background-repeat，所以不能从根本解决问题，不过基本可以满足大部分需求了。