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：
1 function correctPNG() { 2 for (var i = 0; i < document.images.length; i++) { 3 var img = document.images[i]; 4 var imgName = img.src.toUpperCase(); 5 if (imgName.substring(imgName.length - 3, imgName.length) == "PNG") { 6 var imgID = (img.id) ? "id='" + img.id + "' " : ""; 7 var imgClass = (img.className) ? "class='" + img.className + "' " : ""; 8 var imgTitle = (img.title) ? "title='" + img.title + "' " : "title='" + img.alt + "' "; 9 var imgStyle = "display:inline-block;" + img.style.cssText; 10 if (img.align == "left") { 11 imgStyle = "float:left;" + imgStyle; 12 } 13 if (img.align == "right") { 14 imgStyle = "float:right;" + imgStyle; 15 } 16 if (img.parentElement.href) { 17 imgStyle = "cursor:hand;" + imgStyle; 18 } 19 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>"; 20 img.outerHTML = strNewHTML; 21 i = i - 1; 22 } 23 } 24 } 25 function alphaBackgrounds() { 26 var rslt = navigator.appVersion.match(/MSIE(d+.d+)/, ''); 27 var itsAllGood = (rslt !== null && Number(rslt[1]) >= 5.5); 28 for (i = 0; i < document.all.length; i++) { 29 var bg = document.all[i].currentStyle.backgroundImage; 30 if (bg) { 31 if (bg.match(/.png/i) !== null) { 32 var mypng = bg.substring(5, bg.length - 2); 33 document.all[i].style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(src ='" + 34 mypng + "',sizingMethod='crop')"; 35 document.all[i].style.backgroundImage = "url('')"; 36 } 37 } 38 } 39 } 40 if (navigator.userAgent.indexOf("MSIE 6.0") > -1) { 41 window.attachEvent("onload", correctPNG); 42 window.attachEvent("onload", alphaBackgrounds); 43 }
第二种：
1）添加以下代码：
1 var DD_belatedPNG = { 2 ns: 'DD_belatedPNG', 3 imgSize: {}, 4 delay: 10, 5 nodesFixed: 0, 6 createVmlNameSpace: function () { /* enable VML */ 7 if (document.namespaces && !document.namespaces[this.ns]) { 8 document.namespaces.add(this.ns, 'urn:schemas-microsoft-com:vml'); 9 } 10 }, 11 createVmlStyleSheet: function () { /* style VML, enable behaviors */ 12 /* 13 Just in case lots of other developers have added 14 lots of other stylesheets using document.createStyleSheet 15 and hit the 31-limit mark, let's not use that method! 16 further reading: http://msdn.microsoft.com/en-us/library/ms531194(VS.85).aspx 17 */ 18 var screenStyleSheet, printStyleSheet; 19 screenStyleSheet = document.createElement('style'); 20 screenStyleSheet.setAttribute('media', 'screen'); 21 document.documentElement.firstChild.insertBefore(screenStyleSheet, document.documentElement.firstChild.firstChild); 22 if (screenStyleSheet.styleSheet) { 23 screenStyleSheet = screenStyleSheet.styleSheet; 24 screenStyleSheet.addRule(this.ns + '\\:*', '{behavior:url(#default#VML)}'); 25 screenStyleSheet.addRule(this.ns + '\\:shape', 'position:absolute;'); 26 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/ */ 27 this.screenStyleSheet = screenStyleSheet; 28 29 /* Add a print-media stylesheet, for preventing VML artifacts from showing up in print (including preview). */ 30 /* Thanks to R閙i Pr関ost for automating this! */ 31 printStyleSheet = document.createElement('style'); 32 printStyleSheet.setAttribute('media', 'print'); 33 document.documentElement.firstChild.insertBefore(printStyleSheet, document.documentElement.firstChild.firstChild); 34 printStyleSheet = printStyleSheet.styleSheet; 35 printStyleSheet.addRule(this.ns + '\\:*', '{display: none !important;}'); 36 printStyleSheet.addRule('img.' + this.ns + '_sizeFinder', '{display: none !important;}'); 37 } 38 }, 39 readPropertyChange: function () { 40 var el, display, v; 41 el = event.srcElement; 42 if (!el.vmlInitiated) { 43 return; 44 } 45 if (event.propertyName.search('background') != -1 || event.propertyName.search('border') != -1) { 46 DD_belatedPNG.applyVML(el); 47 } 48 if (event.propertyName == 'style.display') { 49 display = (el.currentStyle.display == 'none') ? 'none' : 'block'; 50 for (v in el.vml) { 51 if (el.vml.hasOwnProperty(v)) { 52 el.vml[v].shape.style.display = display; 53 } 54 } 55 } 56 if (event.propertyName.search('filter') != -1) { 57 DD_belatedPNG.vmlOpacity(el); 58 } 59 }, 60 vmlOpacity: function (el) { 61 if (el.currentStyle.filter.search('lpha') != -1) { 62 var trans = el.currentStyle.filter; 63 trans = parseInt(trans.substring(trans.lastIndexOf('=')+1, trans.lastIndexOf(')')), 10)/100; 64 el.vml.color.shape.style.filter = el.currentStyle.filter; /* complete guesswork */ 65 el.vml.image.fill.opacity = trans; /* complete guesswork */ 66 } 67 }, 68 handlePseudoHover: function (el) { 69 setTimeout(function () { /* wouldn't work as intended without setTimeout */ 70 DD_belatedPNG.applyVML(el); 71 }, 1); 72 }, 73 /** 74 * This is the method to use in a document. 75 * @param {String} selector - REQUIRED - a CSS selector, such as '#doc .container' 76 **/ 77 fix: function (selector) { 78 if (this.screenStyleSheet) { 79 var selectors, i; 80 selectors = selector.split(','); /* multiple selectors supported, no need for multiple calls to this anymore */ 81 for (i=0; i<selectors.length; i++) { 82 this.screenStyleSheet.addRule(selectors[i], 'behavior:expression(DD_belatedPNG.fixPng(this))'); /* seems to execute the function without adding it to the stylesheet - interesting... */ 83 } 84 } 85 }, 86 applyVML: function (el) { 87 el.runtimeStyle.cssText = ''; 88 this.vmlFill(el); 89 this.vmlOffsets(el); 90 this.vmlOpacity(el); 91 if (el.isImg) { 92 this.copyImageBorders(el); 93 } 94 }, 95 attachHandlers: function (el) { 96 var self, handlers, handler, moreForAs, a, h; 97 self = this; 98 handlers = {resize: 'vmlOffsets', move: 'vmlOffsets'}; 99 if (el.nodeName == 'A') { 100 moreForAs = {mouseleave: 'handlePseudoHover', mouseenter: 'handlePseudoHover', focus: 'handlePseudoHover', blur: 'handlePseudoHover'}; 101 for (a in moreForAs) { 102 if (moreForAs.hasOwnProperty(a)) { 103 handlers[a] = moreForAs[a]; 104 } 105 } 106 } 107 for (h in handlers) { 108 if (handlers.hasOwnProperty(h)) { 109 handler = function () { 110 self[handlers[h]](el); 111 }; 112 el.attachEvent('on' + h, handler); 113 } 114 } 115 el.attachEvent('onpropertychange', this.readPropertyChange); 116 }, 117 giveLayout: function (el) { 118 el.style.zoom = 1; 119 if (el.currentStyle.position == 'static') { 120 el.style.position = 'relative'; 121 } 122 }, 123 copyImageBorders: function (el) { 124 var styles, s; 125 styles = {'borderStyle':true, 'borderWidth':true, 'borderColor':true}; 126 for (s in styles) { 127 if (styles.hasOwnProperty(s)) { 128 el.vml.color.shape.style[s] = el.currentStyle[s]; 129 } 130 } 131 }, 132 vmlFill: function (el) { 133 if (!el.currentStyle) { 134 return; 135 } else { 136 var elStyle, noImg, lib, v, img, imgLoaded; 137 elStyle = el.currentStyle; 138 } 139 for (v in el.vml) { 140 if (el.vml.hasOwnProperty(v)) { 141 el.vml[v].shape.style.zIndex = elStyle.zIndex; 142 } 143 } 144 el.runtimeStyle.backgroundColor = ''; 145 el.runtimeStyle.backgroundImage = ''; 146 noImg = true; 147 if (elStyle.backgroundImage != 'none' || el.isImg) { 148 if (!el.isImg) { 149 el.vmlBg = elStyle.backgroundImage; 150 el.vmlBg = el.vmlBg.substr(5, el.vmlBg.lastIndexOf('")')-5); 151 } 152 else { 153 el.vmlBg = el.src; 154 } 155 lib = this; 156 if (!lib.imgSize[el.vmlBg]) { /* determine size of loaded image */ 157 img = document.createElement('img'); 158 lib.imgSize[el.vmlBg] = img; 159 img.className = lib.ns + '_sizeFinder'; 160 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! */ 161 imgLoaded = function () { 162 this.width = this.offsetWidth; /* weird cache-busting requirement! */ 163 this.height = this.offsetHeight; 164 lib.vmlOffsets(el); 165 }; 166 img.attachEvent('onload', imgLoaded); 167 img.src = el.vmlBg; 168 img.removeAttribute('width'); 169 img.removeAttribute('height'); 170 document.body.insertBefore(img, document.body.firstChild); 171 } 172 el.vml.image.fill.src = el.vmlBg; 173 noImg = false; 174 } 175 el.vml.image.fill.on = !noImg; 176 el.vml.image.fill.color = 'none'; 177 el.vml.color.shape.style.backgroundColor = elStyle.backgroundColor; 178 el.runtimeStyle.backgroundImage = 'none'; 179 el.runtimeStyle.backgroundColor = 'transparent'; 180 }, 181 /* 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 */ 182 vmlOffsets: function (el) { 183 var thisStyle, size, fudge, makeVisible, bg, bgR, dC, altC, b, c, v; 184 thisStyle = el.currentStyle; 185 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}; 186 fudge = (size.L + size.bLW == 1) ? 1 : 0; 187 /* vml shape, left, top, width, height, origin */ 188 makeVisible = function (vml, l, t, w, h, o) { 189 vml.coordsize = w+','+h; 190 vml.coordorigin = o+','+o; 191 vml.path = 'm0,0l'+w+',0l'+w+','+h+'l0,'+h+' xe'; 192 vml.style.width = w + 'px'; 193 vml.style.height = h + 'px'; 194 vml.style.left = l + 'px'; 195 vml.style.top = t + 'px'; 196 }; 197 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); 198 makeVisible(el.vml.image.shape, (size.L + size.bLW), (size.T + size.bTW), (size.W), (size.H), 1 ); 199 bg = {'X':0, 'Y':0}; 200 if (el.isImg) { 201 bg.X = parseInt(thisStyle.paddingLeft, 10) + 1; 202 bg.Y = parseInt(thisStyle.paddingTop, 10) + 1; 203 } 204 else { 205 for (b in bg) { 206 if (bg.hasOwnProperty(b)) { 207 this.figurePercentage(bg, size, b, thisStyle['backgroundPosition'+b]); 208 } 209 } 210 } 211 el.vml.image.fill.position = (bg.X/size.W) + ',' + (bg.Y/size.H); 212 bgR = thisStyle.backgroundRepeat; 213 dC = {'T':1, 'R':size.W+fudge, 'B':size.H, 'L':1+fudge}; /* these are defaults for repeat of any kind */ 214 altC = { 'X': {'b1': 'L', 'b2': 'R', 'd': 'W'}, 'Y': {'b1': 'T', 'b2': 'B', 'd': 'H'} }; 215 if (bgR != 'repeat' || el.isImg) { 216 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 */ 217 if (bgR.search('repeat-') != -1) { /* now let's revert to dC for repeat-x or repeat-y */ 218 v = bgR.split('repeat-')[1].toUpperCase(); 219 c[altC[v].b1] = 1; 220 c[altC[v].b2] = size[altC[v].d]; 221 } 222 if (c.B > size.H) { 223 c.B = size.H; 224 } 225 el.vml.image.shape.style.clip = 'rect('+c.T+'px '+(c.R+fudge)+'px '+c.B+'px '+(c.L+fudge)+'px)'; 226 } 227 else { 228 el.vml.image.shape.style.clip = 'rect('+dC.T+'px '+dC.R+'px '+dC.B+'px '+dC.L+'px)'; 229 } 230 }, 231 figurePercentage: function (bg, size, axis, position) { 232 var horizontal, fraction; 233 fraction = true; 234 horizontal = (axis == 'X'); 235 switch(position) { 236 case 'left': 237 case 'top': 238 bg[axis] = 0; 239 break; 240 case 'center': 241 bg[axis] = 0.5; 242 break; 243 case 'right': 244 case 'bottom': 245 bg[axis] = 1; 246 break; 247 default: 248 if (position.search('%') != -1) { 249 bg[axis] = parseInt(position, 10) / 100; 250 } 251 else { 252 fraction = false; 253 } 254 } 255 bg[axis] = Math.ceil( fraction ? ( (size[horizontal?'W': 'H'] * bg[axis]) - (size[horizontal?'w': 'h'] * bg[axis]) ) : parseInt(position, 10) ); 256 if (bg[axis] % 2 === 0) { 257 bg[axis]++; 258 } 259 return bg[axis]; 260 }, 261 fixPng: function (el) { 262 el.style.behavior = 'none'; 263 var lib, els, nodeStr, v, e; 264 if (el.nodeName == 'BODY' || el.nodeName == 'TD' || el.nodeName == 'TR') { /* elements not supported yet */ 265 return; 266 } 267 el.isImg = false; 268 if (el.nodeName == 'IMG') { 269 if(el.src.toLowerCase().search(/\.png$/) != -1) { 270 el.isImg = true; 271 el.style.visibility = 'hidden'; 272 } 273 else { 274 return; 275 } 276 } 277 else if (el.currentStyle.backgroundImage.toLowerCase().search('.png') == -1) { 278 return; 279 } 280 lib = DD_belatedPNG; 281 el.vml = {color: {}, image: {}}; 282 els = {shape: {}, fill: {}}; 283 for (v in el.vml) { 284 if (el.vml.hasOwnProperty(v)) { 285 for (e in els) { 286 if (els.hasOwnProperty(e)) { 287 nodeStr = lib.ns + ':' + e; 288 el.vml[v][e] = document.createElement(nodeStr); 289 } 290 } 291 el.vml[v].shape.stroked = false; 292 el.vml[v].shape.appendChild(el.vml[v].fill); 293 el.parentNode.insertBefore(el.vml[v].shape, el); 294 } 295 } 296 el.vml.image.shape.fillcolor = 'none'; /* Don't show blank white shapeangle when waiting for image to load. */ 297 el.vml.image.fill.type = 'tile'; /* Makes image show up. */ 298 el.vml.color.fill.on = false; /* Actually going to apply vml element's style.backgroundColor, so hide the whiteness. */ 299 lib.attachHandlers(el); 300 lib.giveLayout(el); 301 lib.giveLayout(el.offsetParent); 302 el.vmlInitiated = true; 303 lib.applyVML(el); /* Render! */ 304 } 305 }; 306 try { 307 document.execCommand("BackgroundImageCache", false, true); /* TredoSoft Multiple IE doesn't like this, so try{} it */ 308 } catch(r) {} 309 DD_belatedPNG.createVmlNameSpace(); 310 DD_belatedPNG.createVmlStyleSheet();
2）第二步在调用：
1 <!--[if IE 6]> 2 <script src="js/DD_belatedPNG.js" mce_src="DD_belatedPNG.js"></script> 3 <script type="text/javascript"> 4 DD_belatedPNG.fix('.class');//这里是CSS选择，多个就有分号“，”隔开； 5 如：DD_belatedPNG.fix('.class1,.class2,.class3') 6 </script> 7 <![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。
