• IE6中 PNG 背景透明的最佳解决方案


    为什么要使用 PNG 图片?

    简单来说,使用 PNG 格式比起 GIF 来表现色彩更丰富,特别是表现渐变以及背景透明的渐变要比GIF格式出色很多。目前,最新的浏览器基本上都支持PNG格式。唯独有万恶的 IE6 不支持 PNG 背景透明,在 IE6 中的 PNG 背景图会显示一个灰色的背景。

    IE6 中 PNG 背景图片透明的方法

    其实方法有很多,但网络上提供的方法也有诸多缺陷。比如不支持 css 中 backgrond-position 与 background-repeat 等,所以园子推荐你使用 DD_belatedPNG,方法如下:

    1.首先下载 DD_belatedPNG.js 文件,本文下方有提供下载,将此文件放置到你的网站中的 js 目录下。

    2.在你使用了 PNG 背景的页面头部嵌入以下代码,一般是加在 head 区域。

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    <!--[if IE 6]>   
    <script src="js/DD_belatedPNG.js" mce_src="DD_belatedPNG.js"></script>   
    <script type="text/javascript">     
     /* EXAMPLE */   
     DD_belatedPNG.fix('.png_bg');   
    /* 将 .png_bg 改成你应用了透明PNG的CSS选择器,例如我例子中的'.trans'*/   
    </script> 
    <![endif]-->

    需要注意的一些问题:

    1.如果你放置的 DD_belatedPNG.js 路径不同的话,也需要更改上述代码中的路径。

    2.以上代码中的

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    DD_belatedPNG.fix('.png_bg');

    括号中的 .png_bg 改成你在 CSS 定义了 PNG 背景图片的选择器,多个选择器请用英文逗号隔开,如下行代码所示:

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    DD_belatedPNG.fix('.png_bg1, .png_bg2');

    3.有些朋友可能需要用到透明的 PNG 图片做为鼠标经过时的背景图片,这就需要用到 a:hover 属性,在这种情况下就需要以“a:hover”来做选择器了,你可以参考下面代码的写法:

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    <!--[if IE 6]>   
    <script type="text/javascript" src="js/DD_belatedPNG.js" ></script>   
    <script type="text/javascript">
    DD_belatedPNG.fix('.trans,.box a:hover');   
    </script>   
    <![endif]-->

    下面是DD_belatedPNG.js修正了一些IE6BUG的代码:

      1 /**
      2 * DD_belatedPNG: Adds IE6 support: PNG images for CSS background-image and HTML <IMG/>.
      3 * Author: Drew Diller
      4 * Email: drew.diller@gmail.com
      5 * URL: http://www.dillerdesign.com/experiment/DD_belatedPNG/
      6 * Version: 0.0.8a
      7 * Licensed under the MIT License: http://dillerdesign.com/experiment/DD_belatedPNG/#license
      8 *
      9 * Example usage:
     10 * DD_belatedPNG.fix('.png_bg'); // argument is a CSS selector
     11 * DD_belatedPNG.fixPng( someNode ); // argument is an HTMLDomElement
     12 **/
     13 
     14 /*
     15 PLEASE READ:
     16 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!
     17 */
     18 
     19 var DD_belatedPNG = {
     20     ns: 'DD_belatedPNG',
     21     imgSize: {},
     22     delay: 10,
     23     nodesFixed: 0,
     24     createVmlNameSpace: function () { /* enable VML */
     25         if (document.namespaces && !document.namespaces[this.ns]) {
     26             document.namespaces.add(this.ns, 'urn:schemas-microsoft-com:vml');
     27         }
     28     },
     29     createVmlStyleSheet: function () { /* style VML, enable behaviors */
     30         /*
     31             Just in case lots of other developers have added
     32             lots of other stylesheets using document.createStyleSheet
     33             and hit the 31-limit mark, let's not use that method!
     34             further reading: http://msdn.microsoft.com/en-us/library/ms531194(VS.85).aspx
     35         */
     36         var screenStyleSheet, printStyleSheet;
     37         screenStyleSheet = document.createElement('style');
     38         screenStyleSheet.setAttribute('media', 'screen');
     39         document.documentElement.firstChild.insertBefore(screenStyleSheet, document.documentElement.firstChild.firstChild);
     40         if (screenStyleSheet.styleSheet) {
     41             screenStyleSheet = screenStyleSheet.styleSheet;
     42             screenStyleSheet.addRule(this.ns + '\:*', '{behavior:url(#default#VML)}');
     43             screenStyleSheet.addRule(this.ns + '\:shape', 'position:absolute;');
     44             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/ */
     45             this.screenStyleSheet = screenStyleSheet;
     46             
     47             /* Add a print-media stylesheet, for preventing VML artifacts from showing up in print (including preview). */
     48             /* Thanks to R閙i Pr関ost for automating this! */
     49             printStyleSheet = document.createElement('style');
     50             printStyleSheet.setAttribute('media', 'print');
     51             document.documentElement.firstChild.insertBefore(printStyleSheet, document.documentElement.firstChild.firstChild);
     52             printStyleSheet = printStyleSheet.styleSheet;
     53             printStyleSheet.addRule(this.ns + '\:*', '{display: none !important;}');
     54             printStyleSheet.addRule('img.' + this.ns + '_sizeFinder', '{display: none !important;}');
     55         }
     56     },
     57     readPropertyChange: function () {
     58         var el, display, v;
     59         el = event.srcElement;
     60         if (!el.vmlInitiated) {
     61             return;
     62         }
     63         if (event.propertyName.search('background') != -1 || event.propertyName.search('border') != -1) {
     64             DD_belatedPNG.applyVML(el);
     65         }
     66         if (event.propertyName == 'style.display') {
     67             display = (el.currentStyle.display == 'none') ? 'none' : 'block';
     68             for (v in el.vml) {
     69                 if (el.vml.hasOwnProperty(v)) {
     70                     el.vml[v].shape.style.display = display;
     71                 }
     72             }
     73         }
     74         if (event.propertyName.search('filter') != -1) {
     75             DD_belatedPNG.vmlOpacity(el);
     76         }
     77     },
     78     vmlOpacity: function (el) {
     79         if (el.currentStyle.filter.search('lpha') != -1) {
     80             var trans = el.currentStyle.filter;
     81             trans = parseInt(trans.substring(trans.lastIndexOf('=')+1, trans.lastIndexOf(')')), 10)/100;
     82             el.vml.color.shape.style.filter = el.currentStyle.filter; /* complete guesswork */
     83             el.vml.image.fill.opacity = trans; /* complete guesswork */
     84         }
     85     },
     86     handlePseudoHover: function (el) {
     87         setTimeout(function () { /* wouldn't work as intended without setTimeout */
     88             DD_belatedPNG.applyVML(el);
     89         }, 1);
     90     },
     91     /**
     92     * This is the method to use in a document.
     93     * @param {String} selector - REQUIRED - a CSS selector, such as '#doc .container'
     94     **/
     95     fix: function (selector) {
     96         if (this.screenStyleSheet) {
     97             var selectors, i;
     98             selectors = selector.split(','); /* multiple selectors supported, no need for multiple calls to this anymore */
     99             for (i=0; i<selectors.length; i++) {
    100                 this.screenStyleSheet.addRule(selectors[i], 'behavior:expression(DD_belatedPNG.fixPng(this))'); /* seems to execute the function without adding it to the stylesheet - interesting... */
    101             }
    102         }
    103     },
    104     applyVML: function (el) {
    105         el.runtimeStyle.cssText = '';
    106         this.vmlFill(el);
    107         this.vmlOffsets(el);
    108         this.vmlOpacity(el);
    109         if (el.isImg) {
    110             this.copyImageBorders(el);
    111         }
    112     },
    113     attachHandlers: function (el) {
    114         var self, handlers, handler, moreForAs, a, h;
    115         self = this;
    116         handlers = {resize: 'vmlOffsets', move: 'vmlOffsets'};
    117         if (el.nodeName == 'A') {
    118             moreForAs = {mouseleave: 'handlePseudoHover', mouseenter: 'handlePseudoHover', focus: 'handlePseudoHover', blur: 'handlePseudoHover'};
    119             for (a in moreForAs) {            
    120                 if (moreForAs.hasOwnProperty(a)) {
    121                     handlers[a] = moreForAs[a];
    122                 }
    123             }
    124         }
    125         for (h in handlers) {
    126             if (handlers.hasOwnProperty(h)) {
    127                 handler = function () {
    128                     self[handlers[h]](el);
    129                 };
    130                 el.attachEvent('on' + h, handler);
    131             }
    132         }
    133         el.attachEvent('onpropertychange', this.readPropertyChange);
    134     },
    135     giveLayout: function (el) {
    136          el.style.zoom = 1;
    137                 if (el.currentStyle.position == 'static') {
    138                 var tags=el.nodeName.toLowerCase();
    139                 if(tags!='html' && tags!='a'&& tags!='img'){
    140                     el.style.position = 'relative'
    141                     };
    142             }
    143     },
    144     copyImageBorders: function (el) {
    145         var styles, s;
    146         styles = {'borderStyle':true, 'borderWidth':true, 'borderColor':true};
    147         for (s in styles) {
    148             if (styles.hasOwnProperty(s)) {
    149                 el.vml.color.shape.style[s] = el.currentStyle[s];
    150             }
    151         }
    152     },
    153     vmlFill: function (el) {
    154         if (!el.currentStyle) {
    155             return;
    156         } else {
    157             var elStyle, noImg, lib, v, img, imgLoaded;
    158             elStyle = el.currentStyle;
    159         }
    160         for (v in el.vml) {
    161             if (el.vml.hasOwnProperty(v)) {
    162                 el.vml[v].shape.style.zIndex = elStyle.zIndex;
    163             }
    164         }
    165         el.runtimeStyle.backgroundColor = '';
    166         el.runtimeStyle.backgroundImage = '';
    167         noImg = true;
    168         if (elStyle.backgroundImage != 'none' || el.isImg) {
    169             if (!el.isImg) {
    170                 el.vmlBg = elStyle.backgroundImage;
    171                 el.vmlBg = el.vmlBg.substr(5, el.vmlBg.lastIndexOf('")')-5);
    172             }
    173             else {
    174                 el.vmlBg = el.src;
    175             }
    176             lib = this;
    177             if (!lib.imgSize[el.vmlBg]) { /* determine size of loaded image */
    178                 img = document.createElement('img');
    179                 lib.imgSize[el.vmlBg] = img;
    180                 img.className = lib.ns + '_sizeFinder';
    181                 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! */
    182                 imgLoaded = function () {
    183                     this.width = this.offsetWidth; /* weird cache-busting requirement! */
    184                     this.height = this.offsetHeight;
    185                     lib.vmlOffsets(el);
    186                 };
    187                 img.attachEvent('onload', imgLoaded);
    188                 img.src = el.vmlBg;
    189                 img.removeAttribute('width');
    190                 img.removeAttribute('height');
    191                 document.body.insertBefore(img, document.body.firstChild);
    192             }
    193             el.vml.image.fill.src = el.vmlBg;
    194             noImg = false;
    195         }
    196         el.vml.image.fill.on = !noImg;
    197         el.vml.image.fill.color = 'none';
    198         el.vml.color.shape.style.backgroundColor = elStyle.backgroundColor;
    199         el.runtimeStyle.backgroundImage = 'none';
    200         el.runtimeStyle.backgroundColor = 'transparent';
    201     },
    202     /* 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 */
    203     vmlOffsets: function (el) {
    204         var thisStyle, size, fudge, makeVisible, bg, bgR, dC, altC, b, c, v;
    205         thisStyle = el.currentStyle;
    206         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};
    207         fudge = (size.L + size.bLW == 1) ? 1 : 0;
    208         /* vml shape, left, top, width, height, origin */
    209         makeVisible = function (vml, l, t, w, h, o) {
    210             vml.coordsize = w+','+h;
    211             vml.coordorigin = o+','+o;
    212             vml.path = 'm0,0l'+w+',0l'+w+','+h+'l0,'+h+' xe';
    213             vml.style.width = w + 'px';
    214             vml.style.height = h + 'px';
    215             vml.style.left = l + 'px';
    216             vml.style.top = t + 'px';
    217         };
    218         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);
    219         makeVisible(el.vml.image.shape, (size.L + size.bLW), (size.T + size.bTW), (size.W), (size.H), 1 );
    220         bg = {'X':0, 'Y':0};
    221         if (el.isImg) {
    222             bg.X = parseInt(thisStyle.paddingLeft, 10) + 1;
    223             bg.Y = parseInt(thisStyle.paddingTop, 10) + 1;
    224         }
    225         else {
    226             for (b in bg) {
    227                 if (bg.hasOwnProperty(b)) {
    228                     this.figurePercentage(bg, size, b, thisStyle['backgroundPosition'+b]);
    229                 }
    230             }
    231         }
    232         el.vml.image.fill.position = (bg.X/size.W) + ',' + (bg.Y/size.H);
    233         bgR = thisStyle.backgroundRepeat;
    234         dC = {'T':1, 'R':size.W+fudge, 'B':size.H, 'L':1+fudge}; /* these are defaults for repeat of any kind */
    235         altC = { 'X': {'b1': 'L', 'b2': 'R', 'd': 'W'}, 'Y': {'b1': 'T', 'b2': 'B', 'd': 'H'} };
    236         if (bgR != 'repeat' || el.isImg) {
    237             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 */
    238             if (bgR.search('repeat-') != -1) { /* now let's revert to dC for repeat-x or repeat-y */
    239                 v = bgR.split('repeat-')[1].toUpperCase();
    240                 c[altC[v].b1] = 1;
    241                 c[altC[v].b2] = size[altC[v].d];
    242             }
    243             if (c.B > size.H) {
    244                 c.B = size.H;
    245             }
    246             el.vml.image.shape.style.clip = 'rect('+c.T+'px '+(c.R+fudge)+'px '+c.B+'px '+(c.L+fudge)+'px)';
    247         }
    248         else {
    249             el.vml.image.shape.style.clip = 'rect('+dC.T+'px '+dC.R+'px '+dC.B+'px '+dC.L+'px)';
    250         }
    251     },
    252     figurePercentage: function (bg, size, axis, position) {
    253         var horizontal, fraction;
    254         fraction = true;
    255         horizontal = (axis == 'X');
    256         switch(position) {
    257             case 'left':
    258             case 'top':
    259                 bg[axis] = 0;
    260                 break;
    261             case 'center':
    262                 bg[axis] = 0.5;
    263                 break;
    264             case 'right':
    265             case 'bottom':
    266                 bg[axis] = 1;
    267                 break;
    268             default:
    269                 if (position.search('%') != -1) {
    270                     bg[axis] = parseInt(position, 10) / 100;
    271                 }
    272                 else {
    273                     fraction = false;
    274                 }
    275         }
    276         bg[axis] = Math.ceil(  fraction ? ( (size[horizontal?'W': 'H'] * bg[axis]) - (size[horizontal?'w': 'h'] * bg[axis]) ) : parseInt(position, 10)  );
    277         if (bg[axis] % 2 === 0) {
    278             bg[axis]++;
    279         }
    280         return bg[axis];
    281     },
    282     fixPng: function (el) {
    283         el.style.behavior = 'none';
    284         var lib, els, nodeStr, v, e;
    285         if (el.nodeName == 'BODY' || el.nodeName == 'TD' || el.nodeName == 'TR') { /* elements not supported yet */
    286             return;
    287         }
    288         el.isImg = false;
    289         if (el.nodeName == 'IMG') {
    290             if(/.png(?:W|$)/.test(el.src.toLowerCase())) {
    291                                 el.isImg = true;
    292                                 el.style.visibility = 'hidden';
    293             }
    294             else {
    295                 return;
    296             }
    297         }
    298         else if (el.currentStyle.backgroundImage.toLowerCase().search('.png') == -1) {
    299             return;
    300         }
    301         lib = DD_belatedPNG;
    302         el.vml = {color: {}, image: {}};
    303         els = {shape: {}, fill: {}};
    304         for (v in el.vml) {
    305             if (el.vml.hasOwnProperty(v)) {
    306                 for (e in els) {
    307                     if (els.hasOwnProperty(e)) {
    308                         nodeStr = lib.ns + ':' + e;
    309                         el.vml[v][e] = document.createElement(nodeStr);
    310                     }
    311                 }
    312                 el.vml[v].shape.stroked = false;
    313                 el.vml[v].shape.appendChild(el.vml[v].fill);
    314                 el.parentNode.insertBefore(el.vml[v].shape, el);
    315             }
    316         }
    317         el.vml.image.shape.fillcolor = 'none'; /* Don't show blank white shapeangle when waiting for image to load. */
    318         el.vml.image.fill.type = 'tile'; /* Makes image show up. */
    319         el.vml.color.fill.on = false; /* Actually going to apply vml element's style.backgroundColor, so hide the whiteness. */
    320         lib.attachHandlers(el);
    321         lib.giveLayout(el);
    322         lib.giveLayout(el.offsetParent);
    323         el.vmlInitiated = true;
    324         lib.applyVML(el); /* Render! */
    325     }
    326 };
    327 try {
    328     document.execCommand("BackgroundImageCache", false, true); /* TredoSoft Multiple IE doesn't like this, so try{} it */
    329 } catch(r) {}
    330 DD_belatedPNG.createVmlNameSpace();
    331 DD_belatedPNG.createVmlStyleSheet();
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  • 原文地址:https://www.cnblogs.com/zimin1985/p/3371731.html
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