效果预览：
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<title>JavaScript 颜色梯度和渐变效果</title>
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</script>
<script type="text/javascript">
//获取颜色梯度方法
var ColorGrads = (function(){
//获取颜色梯度数据
function GetStep(start, end, step) {
var colors = [], start = GetColor(start), end = GetColor(end),
stepR = (end[0] - start[0]) / step,
stepG = (end[1] - start[1]) / step,
stepB = (end[2] - start[2]) / step;
//生成颜色集合
for(var i = 0, r = start[0], g = start[1], b = start[2]; i < step; i++){
colors[i] = [r, g, b]; r += stepR; g += stepG; b += stepB;
}
colors[i] = end;
//修正颜色值
return $$A.map(colors, function(x){ return $$A.map(x, function(x){
return Math.min(Math.max(0, Math.floor(x)), 255);
});});
}
//获取颜色数据
var frag;
function GetColor(color) {
var ret = GetData(color);
if (ret === undefined) {
if (!frag) {
frag = document.createElement("textarea");
frag.style.display = "none";
document.body.insertBefore(frag, document.body.childNodes[0]);
};
try { frag.style.color = color; } catch(e) { return [0, 0, 0]; }//ie opera
if (document.defaultView) {
//opera #rrggbb
ret = GetData(document.defaultView.getComputedStyle(frag, null).color);
} else {
color = frag.createTextRange().queryCommandValue("ForeColor");
ret = [ color & 0x0000ff, (color & 0x00ff00) >>> 8, (color & 0xff0000) >>> 16 ];
}
}
return ret;
}
//获取颜色数组
function GetData(color) {
var re = RegExp;
if (/^#([0-9a-f]{2})([0-9a-f]{2})([0-9a-f]{2})$/i.test(color)) {
//#rrggbb
return $$A.map([ re.$1, re.$2, re.$3 ], function(x){
return parseInt(x, 16);
});
} else if (/^#([0-9a-f])([0-9a-f])([0-9a-f])$/i.test(color)) {
//#rgb
return $$A.map([ re.$1, re.$2, re.$3 ], function(x){
return parseInt(x + x, 16);
});
} else if (/^rgb((.*),(.*),(.*))$/i.test(color)) {
//rgb(n,n,n) or rgb(n%,n%,n%)
return $$A.map([ re.$1, re.$2, re.$3 ], function(x){
return x.indexOf("%") > 0 ? parseFloat(x, 10) * 2.55 : x | 0;
});
}
}
return function(colors, step){
var ret = [], len = colors.length;
if ( step === undefined ) { step = 20; }
if ( len == 1 ) {
ret = GetStep( colors[0], colors[0], step );
} else if ( len > 1 ) {
for(var i = 0, n = len - 1; i < n; i++){
var steps = GetStep( colors[i], colors[i+1], step );
i < n - 1 && steps.pop();
ret = ret.concat(steps);
}
}
return ret;
}
})();
//渐变对象
var ColorTrans = function(elem, options){
this._elem = $$(elem);
this._timer = null;//定时器
this._index = 0;//索引
this._colors = [];//颜色集合
this._options = {};//参数对象
this._setOptions(options);
this.speed = Math.abs(this.options.speed);
this.style = this.options.style;
this.reset({
from: this.options.from || $$D.getStyle(this._elem, this.style),
to: this.options.to,
step: Math.abs(this.options.step)
});
this._set();
};
ColorTrans.prototype = {
//设置默认属性
_setOptions: function(options) {
this.options = {//默认值
from: "",//开始颜色(默认空值方便自动获取)
to: "#000",//结束颜色
step: 20,//渐变级数
speed: 20,//渐变速度
style: "color"//设置属性（Scripting属性）
};
$$.extend(this.options, options || {});
},
//重设颜色集合
reset: function(options) {
//根据参数设置属性
this._options = options = $$.extend( this._options, options || {} );
//获取颜色集合
this._colors = ColorGrads( [ options.from, options.to ], options.step );
this._index = 0;
},
//颜色渐入
transIn: function() {
this.stop(); this._index++; this._set();
if(this._index < this._colors.length - 1){
this._timer = setTimeout($$F.bind( this.transIn, this ), this.speed);
}
},
//颜色渐出
transOut: function() {
this.stop(); this._index--; this._set();
if(this._index > 0){
this._timer = setTimeout($$F.bind( this.transOut, this ), this.speed);
}
},
//颜色设置
_set: function() {
var color = this._colors[Math.min(Math.max(0, this._index), this._colors.length - 1)];
this._elem.style[this.style] = "rgb(" + color.join(",") + ")";
},
//停止
stop: function() {
clearTimeout(this._timer);
}
};
</script>
</head>
<body>
<style type="text/css">
#idGrads div{height:1px;overflow:hidden;}
</style>
颜色梯度变化演示：
<div id="idGrads"> </div>
<Br />
<input id="idGradsColor" type="text" value="green"/>
<input id="idGradsSet" type="button" value="设置颜色">
<script>
($$("idGradsSet").onclick = function(){
var colors = ColorGrads( ["#fff", $$("idGradsColor").value], 50 );
$$("idGrads").innerHTML = $$A.map(colors.concat().concat(colors.reverse()), function(x){
return "<div style='background:rgb(" + x.join(",") + ")'></div>";
}).join("");
})()
</script>
<Br />
<Br />
<style type="text/css">
#idPicker ul{float:left;}
#idPicker li{overflow:hidden;width:10px;height:10px;line-height:0;font-size:0;}
#idPicker li.on{width:8px;height:8px; border:1px solid #000;}
#idPicker ul, #idPicker li{list-style:none;margin:0;padding:0;}
#idPicker:after{content:".";display:block;visibility:hidden;height:0;clear:both;}
#idPicker{zoom:1;}
</style>
简单的颜色拾取器： <Br />
选择颜色： <span id="idPickerShow"> </span>
<div id="idPicker"> </div>
<script>
$$("idPicker").innerHTML = "<ul>" +
$$A.map(ColorGrads( ["red", "yellow", "blue"], 10 ), function(x){
return $$A.map(ColorGrads( ["#fff", "rgb(" + x.join(",") + ")" ,"#000"], 10 ),
function(x){
return "<li style='background:rgb(" + x.join(",") + ")'></li>";
}
).join("");
}).join("</ul><ul>") + "</ul>";
var oPickerShow = $$("idPickerShow");
$$A.forEach($$("idPicker").getElementsByTagName("li"), function(li){
li.onmouseover = function(){
this.className = "on";
oPickerShow.innerHTML = oPickerShow.style.backgroundColor
= this.style.backgroundColor;
}
li.onmouseout = function(){ this.className = ""; }
})
</script>
<Br />
<Br />
<style type="text/css">
#idMenu{ background:#DBDBDB;text-align:center;line-height:25px; table-layout:fixed;}
#idMenu td{ cursor:pointer; color:#666; background:#f6f6f6;}
</style>
颜色渐变菜单：
<table id="idMenu" width="600" border="0" cellspacing="5" cellpadding="0">
<tr>
<td><a href="http://www.cnblogs.com/cloudgamer/archive/2008/07/21/ImgCropper.html">Cropper</a></td>
<td><a href="http://www.cnblogs.com/cloudgamer/archive/2009/01/06/Tween.html">Tween</a></td>
<td><a href="http://www.cnblogs.com/cloudgamer/archive/2008/12/24/Slider.html">Slider</a></td>
<td><a href="http://www.cnblogs.com/cloudgamer/archive/2008/12/03/Resize.html">Resize</a></td>
<td><a href="http://www.cnblogs.com/cloudgamer/archive/2008/11/17/Drag.html">Drag</a></td>
<td><a href="http://www.cnblogs.com/cloudgamer/archive/2009/07/07/FixedTips.html">Tooltips</a></td>
</tr>
</table>
<script>
$$A.forEach($$("idMenu").getElementsByTagName("td"), function(x, i){
var a = x.getElementsByTagName("a")[0], href = a.href, txt = a.innerHTML;
x.onclick = function(){ location.href = href; }
x.innerHTML = txt;
var ct1 = new ColorTrans(x, { to: "white" });
var ct2 = new ColorTrans(x, { to: "rgb(20,150,0)", style: "backgroundColor" });
x.onmouseover = function(){ ct1.transIn(); ct2.transIn(); }
x.onmouseout = function(){ ct1.transOut(); ct2.transOut(); }
})
</script>
<Br />
<Br />
<style type="text/css">
#idRandom{padding:10px; background:#CCC; color:#fff;}
</style>
点击随机颜色渐变：
<div id="idRandom"><b>点击随机换颜色</b></div>
<script>
var ctRandom = new ColorTrans("idRandom", { style: "backgroundColor" }),
ctRandom2 = new ColorTrans("idRandom");
$$("idRandom").onclick = function(){
var rgb = $$A.map([1,1,1], function(){ return Math.floor((Math.random() * 255)); } ),
rgb2 = $$A.map(rgb, function(x){ return 255 - x; } );
ctRandom.reset({ from: this.style.backgroundColor, to: "rgb(" + rgb.join(",") + ")" })
ctRandom.transIn();
ctRandom2.reset({ from: this.style.color, to: "rgb(" + rgb2.join(",") + ")" })
ctRandom2.transIn();
}
</script>
</body>
</html>