项目中经常有遇到需求半透明的情况，如图片、文字、容器、背景等等，每次都要去翻以前的项目，不甚其烦。现在一次性做个小结，方便自己查阅，也同时分享给大家：
一、 元素容器透明
1 .div{2 opacity: 0.5; /* Firefox、Chorme、Opera等主流浏览器识别 */3 filter:alpha(opacity=50); /* IE6及以上IE浏览器识别 */4 } 说明：
1. opacity:* 取值0-1之间，由全透明向不透明递增，超过1之后默认不透明；
2. filter:alpha(opacity= *) 取值0-100之间，与上面同理；
3. 用此属性后，元素容器内子元素全部继承，即全都会跟着半透明。
二、元素背景透明
1 .div{2 background: rgba(0,0,0,.50); /* Firefox、Chorme、Opera等主流浏览器识别 */
3 filter:progid:DXImageTransform.Microsoft.Gradient(startColorStr=#7f000000, endColorStr=#7f000000); /* IE6及以上IE浏览器识别 */ 4 }
说明：
1. background:rgba(m n) 其中m是rgb颜色值，n是透明度，取值1-100之间，与上面第一条同理；
2. startColorStr=m ,endColor=n 其中m和n由两部分组成，前2位是透明度，后面6位是十六色值。如7f代表0.5的透明度，000000就是黑色了（不能简写成000）；
3. 第2点中m=n时是均匀透明，≠时是渐变透明，下面附一组前两个数值对应的透明度数据，格式如 rgb透明值--IEfilter值：
0.1 -- 19 | 0.2 -- 33 | 0.3 -- 4c | 0.4 -- 66 | 0.5 -- 7f | 0.6 -- 99 | 0.7 -- b2 | 0.8 -- c8 | 0.9 -- e5 |
三、 图片透明
说明：其实也就是为了针对IE6。IE7及以上浏览器都直接支持半透明图片。方法有很多，牛人总结了将近7、8种，我常用的是下面这种：
1. 首先去网上下个png.js，或者干脆从这里复制过去保存为js文件吧（声明：非本人所写，但也找不到谁是原创了）
/*** DD_belatedPNG: Adds IE6 support: PNG images for CSS background-image and HTML ![]()
.* Author: Drew Diller* Email: drew.diller@gmail.com* URL: http://www.dillerdesign.com/experiment/DD_belatedPNG/* Version: 0.0.8a* Licensed under the MIT License: http://dillerdesign.com/experiment/DD_belatedPNG/#license** Example usage:* DD_belatedPNG.fix('.png_bg'); // argument is a CSS selector* DD_belatedPNG.fixPng( someNode ); // argument is an HTMLDomElement**//*PLEASE READ:Absolutely everything in this script is SILLY. I know this. IE's rendering of certain pixels doesn't make sense, so neither does this code!*/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?i Pr?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 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. 在你的页面底部，body结束标签和html结束标签之间加载这段话：
3. 然后确保路径不要写错了。最后在DD_belatedPNG.fix("")里面加需要进行半透明处理的图片元素名或者class、ID名就可以了。
四、未完待续。
