兼容多浏览器实现半透明(Opera ie firefox)

Click on a link above to make the image disappear and re-appear by gradually fading in/out. It uses CSS transparency, in CSS you can set the transparency in different ways. To ensure that it works on most browsers we use all three.

opacity: 0.5;

This one is the official CSS3 method, at the moment it works in newer Mozilla versions.

-moz-opacity: 0.5;
This one works in older versions of Mozilla and Phoenix/FireBird/FireFox.

-khtml-opacity: 0.5;

This is used by browsers that use teh KHTML rendering engine, namely Konquerer on Linux and Safari on MacOS.

filter: alpha(opacity=50);

This one works only in MSIE.

There is actually another one: -khtml-opacity: 0.5; works for the browsers Konquerer on Linux and Safari on MacOS. You could add it too if you want to support these users. Somewhere in the near future most browsers will support CSS3 and opacity: 0.5; should work everywhere.

复制代码代码如下:

function opacity(id, opacStart, opacEnd, millisec) {

    //speed for each frame

    var speed = Math.round(millisec / 100);

    var timer = 0;

    //determine the direction for the blending, if start and end are the same nothing happens

    if(opacStart > opacEnd) {

        for(i = opacStart; i >= opacEnd; i–) {

            setTimeout(“changeOpac(” + i + “,'” + id + “‘)”,(timer * speed));

            timer++;

        }

    } else if(opacStart < opacEnd) {

        for(i = opacStart; i <= opacEnd; i++)

            {

            setTimeout(“changeOpac(” + i + “,'” + id + “‘)”,(timer * speed));

            timer++;

        }

    }

}

//change the opacity for different browsers

function changeOpac(opacity, id) {

    var object = document.getElementById(id).style;

    object.opacity = (opacity / 100);

    object.MozOpacity = (opacity / 100);

    object.KhtmlOpacity = (opacity / 100);

    object.filter = “alpha(opacity=” + opacity + “)”;

}

function shiftOpacity(id, millisec) {

    //if an element is invisible, make it visible, else make it ivisible

    if(document.getElementById(id).style.opacity == 0) {

        opacity(id, 0, 100, millisec);

    } else {

        opacity(id, 100, 0, millisec);

    }

}

function blendimage(divid, imageid, imagefile, millisec) {

var speed = Math.round(millisec / 100);

var timer = 0;

//set the current image as background

document.getElementById(divid).style.backgroundImage = “url(” + document.getElementById(imageid).src + “)”;

//make image transparent

changeOpac(0, imageid);

//make new image

document.getElementById(imageid).src = imagefile;

    //fade in image

    for(i = 0; i <= 100; i++) {

        setTimeout(“changeOpac(” + i + “,'” + imageid + “‘)”,(timer * speed));

        timer++;

    }

}

function currentOpac(id, opacEnd, millisec) {

//standard opacity is 100

var currentOpac = 100;

    //if the element has an opacity set, get it

    if(document.getElementById(id).style.opacity < 100) {

        currentOpac = document.getElementById(id).style.opacity * 100;

    }

//call for the function that changes the opacity

opacity(id, currentOpac, opacEnd, millisec)

}

更多参考
http://www.brainerror.net/scripts_js_blendtrans.php

http://realazy.org/blog/2006/03/21/ie-firefox-opera-alpha-transparency/

http://alistapart.com/stories/pngopacity/

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