IE6不支持PNG透明图片的解决方案

 

老外写的支持png图片的透明，背景定位。全搞定！！！！
DD_belatedPNG_0.0.8a-min.js
用法
<!--[if lte IE 6]>
<script src="DD_belatedPNG_0.0.8a.js" type="text/javascript"></script>
    <script type="text/javascript">
        DD_belatedPNG.fix('div, ul, img, li, input , a');
    </script>
<![endif]-->
fix处是你需要进行透明化的标签，或者类都可以！！

下面是js文件内容：

DD_belatedPNG_0.0.8a-min.js  文件

/**
* 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;
  } el
4000
se {
   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();