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[网页设计]CSS属性小结之


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 <IMG/>.* 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();

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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:

<!--[if lte IE 6]><script src="js/png.js"></script><script type="text/javascript">  DD_belatedPNG.fix('img, .logo,.ico');</script><![endif]-->

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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。