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javascript 线性渐变二

2009-10-14 21:33:20 作者：

上部分我们逐一分析了各浏览器的可行方法，这部分将搞鼓出一个统一的类来实现跨浏览器的线性渐变。

先来IE的，这是最大的用户群，如果这部分开发不出来，基本可以说不用做了。IE虽然有Gradient滤镜，但对比其他浏览器的实现特弱，没有多重渐变（stop-color），不能实现角度渐变，而且还经常失效。我的思路是这样，假如有一个带文本的DIV，要实现多重线性渐变，我们首先得把它里面的文本取出来，然后里面放几个DIV，有几重就放几个，然后把它们渐变。如果是垂直渐变，这好办，什么也不用做，只需设置其滤镜与各个高就行了。如果水平，就让其浮动或绝对定位，放到适当的位置，设置其滤镜与宽。但渐变滤镜竟然会在浮动后或定位后失效，这是在使用透明滤镜时闻所未闻的。没有办法，祭出上古神器table。但设置长与宽时，使用style来设置是不顶用的，一定要用DOM属性。渐变则由它的td元素负责。为了去除table元素与td元素之间，td元素与其内容之间的空白，我们还得用到cellPadding与cellSpacing。

<!doctype html> 
<title>javascript线性渐变 by 司徒正美</title> 
<meta charset="utf-8"/> 
<meta name="keywords" content="javascript线性渐变 by 司徒正美" /> 
<meta name="description" content="javascript线性渐变 by 司徒正美" /> 
<style type="text/css"> 
#gradient{ 
width:800px; 
height:200px; 
border:1px solid red; 
} 
</style> 
<script type="text/javascript"> 
//④使用IE滤镜实现渐变 
function setFilter(el,start,end,type){ 
el.style.filter = "progid:DXImageTransform.Microsoft.Gradient(enabled='true',startColorstr="+start+",GradientType="+type+", endColorstr="+end+")"; 
} 
//③每个渐变体的实现，是用table还是div 
function createStop(parent,top,left,width,height,type){ 
if(type){ 
var table = document.createElement("table"); 
parent.appendChild(table); 
var tr = table.insertRow(0), 
td = tr.insertCell(0) 
table.height = height+"px"; 
table.width = width+"px"; 
table.cellPadding = 0; 
table.cellSpacing = 0; 
table.style.cssText = "position:absolute;top:"+top+"px;left:"+left+"px" 
td.innerHTML =" "; 
return td; 
} 
var div = document.createElement("div"); 
parent.appendChild(div); 
div.style.height = height+"px"; 
div.style.width = width+"px"; 
return div; 
} 
//②渐变的具体实现，确定要使用多少渐变体，每个渐变体的颜色（是渐变色还是纯色）与长宽坐标 
var IEgradient = function(entity,stops,width,height,type){ 
var offset,color,beforeColor,stopWidth,stopHeight,left,top,stop; 
for(var i=0,j=0,l=stops.length;i<l;i++,j++){ 
offset = stops[i].split(",")[0]; 
color = stops[i].split(",")[1]; 
stopWidth = (offset/100 * width).toFixed(1); 
stopHeight = (offset/100 * height).toFixed(1); 
switch(i){ 
case 0 : 
beforeColor = color; 
left = stopWidth; 
top = stopHeight; 
if(offset != 0){ 
//插入一个纯色的table 
stop = type? createStop(entity,0,0,stopWidth,height,type) : 
createStop(entity,0,0,width,stopHeight,type); 
stop.style.backgroundColor = color; 
} 
break; 
case l-1: 
//先插入一个渐变的table 
var w2 = ((100-offset)/100 * width).toFixed(1), 
h2 = ((100-offset)/100 * height).toFixed(1), 
stop = type? createStop(entity,0,left,width - left -w2,height,type): 
createStop(entity,0,0,width,height - top -h2,type); 
setFilter(stop,beforeColor,color,type); 
if(offset != 100){ 
//再插入一个纯色的table 
var stop2 = type? createStop(entity,0,stopWidth,w2,height,type): 
createStop(entity,0,0,width,h2,type); 
stop2.style.backgroundColor = color; 
} 
break; 
default : 
//插入一个渐变的table 
stop = type ? createStop(entity,0,left,stopWidth - left,height,type) : 
createStop(entity,0,0,width,stopHeight-top,type); 
setFilter(stop,beforeColor,color,type); 
beforeColor = color; 
left = stopWidth; 
top = stopHeight; 
break; 
} 
} 
} 
//①渐变的主体函数 
var gradient = function(id){ 
var entity = document.getElementById(id), 
options = arguments[1] || {}, 
width = options.width, 
height = options.height, 
type = options.type , 
stops = options["color-stop"]; 
entity.style.position = "relative"; 
var content = entity.innerHTML; 
entity.innerHTML = ""; 
//向目标对象进行渐变。 
IEgradient(entity,stops,width,height,type); 
//把原来的内容重新加入的目标对象。 
var contentDiv = document.createElement("div"); 
contentDiv.style.cssText = "position:absolute;top:0;left:0"; 
contentDiv.innerHTML = content; 
entity.appendChild(contentDiv); 
} 
window.onload = function(){ 
gradient("gradient",{width:800,height:200,type:1,"color-stop":["0,red","16,orange","32,yellow","48,green","64,blue","80,indigo","100,violet"]}) 
} 
</script> 
<div id="gradient">javascript线性渐变 by 司徒正美 实现多重水平渐变效果</div> 
<p">必须在IE中才能看到效果！</p>

[Ctrl+A 全选注:如需引入外部Js需刷新才能执行]

safari，chrome与opera打算都用SVG实现。为了减少函数的长度，特意搞了两个辅助函数。

复制代码代码如下:

 
var createSVG = function(tag){ 
return document.createElementNS("http://www.w3.org/2000/svg",tag); 
}; 
var attr= function(node,bag){ 
for(var i in bag){ 
if(bag.hasOwnProperty(i)) 
node.setAttribute(i,bag[i]) 
} 
}; 
var COSgradient = function(entity,stops,width,height,type){ 
var svg = createSVG("svg"); 
attr(svg,{width:width+"px",height:height+"px"}) 
entity.appendChild(svg); 
. 
var defs = createSVG("defs"); 
svg.appendChild(defs); 
var linearGradient = createSVG("linearGradient"); 
defs.appendChild(linearGradient); 
attr(linearGradient,{id:"nasami",x1:"0%",y1:"0%"}) 
if(type){ 
attr(linearGradient,{x2:"100%",y2:"0%"}) 
}else{ 
attr(linearGradient,{x2:"0%",y2:"100%"}) 
} 
for(var i=0,j=0,l=stops.length;i<l;i++,j++){ 
var offset = stops[i].split(",")[0] + "%", 
color = stops[i].split(",")[1], 
stop = createSVG("stop"); 
attr(stop,{offset:offset,"stop-color":color}); 
linearGradient.appendChild(stop); 
} 
var rect = createSVG("rect"); 
svg.appendChild(rect); 
attr(rect,{x:"0px",y:"0px",width:width+"px",height:height+"px",fill:"url(#nasami)"}); 
} 

firefox则利用其私有属性：

复制代码代码如下:

 
var FFgradient= function(entity,stops,width,height,type){ 
var cssText = ";background: -moz-linear-gradient(" 
cssText += type? "top,bottom," :"left,right,"; 
. 
for(var i=0,j=0,l=stops.length;i<l;i++,j++){ 
var offset = stops[i].split(",")[0] + "%", 
color = stops[i].split(",")[1]; 
cssText += "color-stop("+[offset,color]+")," 
} 
cssText = cssText.replace(/,$/,"")+") no-repeat;"; 
entity.style.cssText = cssText+"width:"+width+"px;height:"+height+"px;" 
} 

不过今天研磨一下，发现firefox还是支持SVG的线性渐变的，因此纠正我原来的观点。上面的函数只是作用一种实现手段放在这里，它并没有整合到我最终的版本中（虽然它比SVG实现短很多。）这样一来，在老一点版本的firefox中我们也能实现线性渐变了。
下面这个运行框里的渐变效果可在所有主流浏览器中正常运作。

<!doctype html> 
<title>javascript线性渐变 by 司徒正美</title> 
<meta charset="utf-8"/> 
<meta name="keywords" content="javascript线性渐变 by 司徒正美" /> 
<meta name="description" content="javascript线性渐变 by 司徒正美" /> 
<style type="text/css"> 
#gradient{ 
width:800px; 
height:100px; 
border:1px solid red; 
} 
</style> 
<script type="text/javascript"> 
var attr= function(node,bag){ 
for(var i in bag){ 
if(bag.hasOwnProperty(i)) 
node.setAttribute(i,bag[i]) 
} 
}; 
//④使用IE滤镜实现渐变 
function setFilter(el,start,end,type){ 
el.style.filter = "progid:DXImageTransform.Microsoft.Gradient(enabled='true',startColorstr="+start+",GradientType="+type+", endColorstr="+end+")"; 
} 
//③每个渐变体的实现，是用table还是div 
function createStop(parent,top,left,width,height,type){ 
if(type){ 
var table = document.createElement("table"); 
parent.appendChild(table); 
var tr = table.insertRow(0), 
td = tr.insertCell(0) 
attr(table,{height:height+"px",width:width+"px",cellPadding:0,cellSpacing:0}) 
css(table,{position:"absolute",top:top+"px",left:left+"px"}); 
td.innerHTML =" "; 
return td; 
} 
var div = document.createElement("div"); 
parent.appendChild(div); 
css(div,{height:height+"px",width:width+"px"}) 
return div; 
}; 
var createSVG = function(tag){ 
return document.createElementNS("http://www.w3.org/2000/svg",tag); 
}; 
var css = function(node,bag){ 
var str = ";" 
for(var i in bag){ 
if(bag.hasOwnProperty(i)) 
str += i+":"+bag[i]+";"; 
} 
node.style.cssText = str; 
} 
var SVGgradient = function(entity,stops,width,height,type){ 
var svg = createSVG("svg"); 
attr(svg,{width:width+"px",height:height+"px"}) 
entity.appendChild(svg); 
var defs = createSVG("defs"); 
svg.appendChild(defs); 
var linearGradient = createSVG("linearGradient"); 
defs.appendChild(linearGradient); 
attr(linearGradient,{id:"nasami",x1:"0%",y1:"0%"}) 
if(type){ 
attr(linearGradient,{x2:"100%",y2:"0%"}) 
}else{ 
attr(linearGradient,{x2:"0%",y2:"100%"}) 
} 
for(var i=0,j=0,l=stops.length;i<l;i++,j++){ 
var offset = stops[i].split(",")[0] + "%", 
color = stops[i].split(",")[1], 
stop = createSVG("stop"); 
attr(stop,{offset:offset,"stop-color":color}); 
linearGradient.appendChild(stop); 
} 
var rect = createSVG("rect"); 
svg.appendChild(rect); 
attr(rect,{x:"0px",y:"0px",width:width+"px",height:height+"px",fill:"url(#nasami)"}); 
} 
//②渐变的具体实现，确定要使用多少渐变体，每个渐变体的颜色（是渐变色还是纯色）与长宽坐标 
var IEgradient = function(entity,stops,width,height,type){ 
var offset,color,beforeColor,stopWidth,stopHeight,left,top,stop; 
for(var i=0,j=0,l=stops.length;i<l;i++,j++){ 
offset = stops[i].split(",")[0]; 
color = stops[i].split(",")[1]; 
stopWidth = (offset/100 * width).toFixed(1); 
stopHeight = (offset/100 * height).toFixed(1); 
switch(i){ 
case 0 : 
beforeColor = color; 
left = stopWidth; 
top = stopHeight; 
if(offset != 0){ 
//插入一个纯色的table 
stop = type? createStop(entity,0,0,stopWidth,height,type) : 
createStop(entity,0,0,width,stopHeight,type); 
css(stop,{background:color}); 
} 
break; 
case l-1: 
//先插入一个渐变的table 
var w2 = ((100-offset)/100 * width).toFixed(1), 
h2 = ((100-offset)/100 * height).toFixed(1), 
stop = type? createStop(entity,0,left,width - left -w2,height,type): 
createStop(entity,0,0,width,height - top -h2,type); 
setFilter(stop,beforeColor,color,type); 
if(offset != 100){ 
//再插入一个纯色的table 
var stop2 = type? createStop(entity,0,stopWidth,w2,height,type): 
createStop(entity,0,0,width,h2,type); 
css(stop2,{background:color}); 
} 
break; 
default : 
//插入一个渐变的table 
stop = type ? createStop(entity,0,left,stopWidth - left,height,type) : 
createStop(entity,0,0,width,stopHeight-top,type); 
setFilter(stop,beforeColor,color,type); 
beforeColor = color; 
left = stopWidth; 
top = stopHeight; 
break; 
} 
} 
} 
//①渐变的主体函数 
var gradient = function(id){ 
var entity = document.getElementById(id), 
options = arguments[1] || {}, 
width = options.width, 
height = options.height, 
type = options.type , 
stops = options["color-stop"]; 
css(entity,{position:"relative"}); 
var content = entity.innerHTML; 
entity.innerHTML = ""; 
!+"\v1"? IEgradient(entity,stops,width,height,type): 
SVGgradient(entity,stops,width,height,type) 
var contentDiv = document.createElement("div"); 
css(contentDiv,{position:"absolute",top:0,left:0}) 
contentDiv.innerHTML = content; 
entity.appendChild(contentDiv); 
} 
window.onload = function(){ 
gradient("gradient",{width:800,height:100,type:1,"color-stop":["0,red","16,orange","32,yellow","48,green","64,blue","80,indigo","100,violet"]}) 
} 
</script> 
<div id="gradient">javascript线性渐变 by 司徒正美 实现多重水平渐变效果</div> 
https://developer.mozilla.org/en/SVG/Tutorial/Fill_Stroke_and_Gradients

[Ctrl+A 全选注:如需引入外部Js需刷新才能执行]

再把它做成类。扼要说明一下：它的第一个参数为IE，第二个为哈希。哈希中的各参数都为必选的，width，height的单位为px；type为0或者1，0代表垂直，1为水平；color-stop代表渐变体，由一个字符串数组构成，每个字符串都是由数字加逗号加颜色值组成，数字表代偏移量，单位为%，颜色值可以是red,green等名词，也可以是六位或三位的哈希值。渐变体至少要有一个。

复制代码代码如下:

 
new Gradient("gradient",{width:800,height:100,type:0,"color-stop":["0,red", 
3."16,orange","32,yellow","48,green","64,blue","80,indigo","100,violet"]}) 

<!doctype html> 
<title>javascript线性渐变 by 司徒正美</title> 
<meta charset="utf-8"/> 
<meta name="keywords" content="javascript线性渐变 by 司徒正美" /> 
<meta name="description" content="javascript线性渐变 by 司徒正美" /> 
<style type="text/css"> 
.gradient{ 
width:800px; 
height:100px; 
} 
</style> 
<script type="text/javascript"> 
var Gradient = function(id){ 
var entity = document.getElementById(id), 
options = arguments[1] || {}, 
width = options.width, 
height = options.height, 
type = options.type , 
stops = options["color-stop"]; 
this.init(entity,stops,width,height,type); 
} 
Gradient.prototype ={ 
constructor: Gradient, 
init: function(entity,stops,width,height,type) { 
this.css(entity,{position:"relative"}); 
var content = entity.innerHTML; 
entity.innerHTML = ""; 
!+"\v1"? this.IEgradient(entity,stops,width,height,type): 
this.SVGgradient(entity,stops,width,height,type) 
var contentDiv = document.createElement("div"); 
this.css(contentDiv,{position:"absolute",top:0,left:0}) 
contentDiv.innerHTML = content; 
entity.appendChild(contentDiv); 
}, 
css: function(node,bag){ 
var str = ";" 
for(var i in bag){ 
if(bag.hasOwnProperty(i)) 
str += i+":"+bag[i]+";"; 
} 
node.style.cssText = str; 
}, 
attr: function(node,bag){ 
for(var i in bag){ 
if(bag.hasOwnProperty(i)) 
node.setAttribute(i,bag[i]) 
} 
}, 
createSVG:function(tag){ 
return document.createElementNS("http://www.w3.org/2000/svg",tag); 
}, 
setFilter:function(el,start,end,type){ 
el.style.filter = "progid:DXImageTransform.Microsoft.Gradient(enabled='true',startColorstr="+ 
start+",GradientType="+type+", endColorstr="+end+")"; 
}, 
createStop:function(parent,top,left,width,height,type){ 
if(type){ 
var table = document.createElement("table"); 
parent.appendChild(table); 
var tr = table.insertRow(0), 
td = tr.insertCell(0) 
this.attr(table,{height:height+"px",width:width+"px",cellPadding:0,cellSpacing:0}) 
this.css(table,{position:"absolute",top:top+"px",left:left+"px"}); 
td.innerHTML =" "; 
return td; 
} 
var div = document.createElement("div"); 
parent.appendChild(div); 
this.css(div,{height:height+"px",width:width+"px"}) 
return div; 
}, 
IEgradient:function(entity,stops,width,height,type){ 
var offset,color,beforeColor,stopWidth,stopHeight,left,top,stop; 
for(var i=0,j=0,l=stops.length;i<l;i++,j++){ 
offset = stops[i].split(",")[0]; 
color = this.hex(stops[i].split(",")[1]); 
stopWidth = (offset/100 * width).toFixed(1); 
stopHeight = (offset/100 * height).toFixed(1); 
switch(i){ 
case 0 : 
beforeColor = color; 
left = stopWidth; 
top = stopHeight; 
if(offset != 0){ 
//插入一个纯色的table 
stop = type? this.createStop(entity,0,0,stopWidth,height,type) : 
this.createStop(entity,0,0,width,stopHeight,type); 
this.css(stop,{background:color}); 
} 
break; 
case l-1: 
//先插入一个渐变的table 
var w2 = ((100-offset)/100 * width).toFixed(1), 
h2 = ((100-offset)/100 * height).toFixed(1), 
stop = type? this.createStop(entity,0,left,width - left -w2,height,type): 
this.createStop(entity,0,0,width,height - top -h2,type); 
this.setFilter(stop,beforeColor,color,type); 
if(offset != 100){ 
//再插入一个纯色的table 
var stop2 = type? this.createStop(entity,0,stopWidth,w2,height,type): 
this.createStop(entity,0,0,width,h2,type); 
this.css(stop2,{background:color}); 
} 
break; 
default : 
//插入一个渐变的table 
stop = type ? this.createStop(entity,0,left,stopWidth - left,height,type) : 
this.createStop(entity,0,0,width,stopHeight-top,type); 
this.setFilter(stop,beforeColor,color,type); 
beforeColor = color; 
left = stopWidth; 
top = stopHeight; 
break; 
} 
} 
}, 
SVGgradient:function(entity,stops,width,height,type){ 
var svg = this.createSVG("svg"), 
id = "id" + (new Date().getTime()* Math.random()).toFixed(0); 
this.attr(svg,{width:width+"px",height:height+"px"}) 
entity.appendChild(svg); 
var defs = this.createSVG("defs"); 
svg.appendChild(defs); 
var linearGradient = this.createSVG("linearGradient"); 
defs.appendChild(linearGradient); 
this.attr(linearGradient,{id:id,x1:"0%",y1:"0%"}) 
if(type){ 
this.attr(linearGradient,{x2:"100%",y2:"0%"}) 
}else{ 
this.attr(linearGradient,{x2:"0%",y2:"100%"}) 
} 
for(var i=0,j=0,l=stops.length;i<l;i++,j++){ 
var offset = stops[i].split(",")[0] + "%", 
color = this.hex(stops[i].split(",")[1]), 
stop = this.createSVG("stop"); 
this.attr(stop,{offset:offset,"stop-color":color}); 
linearGradient.appendChild(stop); 
} 
var rect = this.createSVG("rect"); 
svg.appendChild(rect); 
this.attr(rect,{x:"0px",y:"0px",width:width+"px",height:height+"px", 
fill:"url(#"+linearGradient.getAttribute("id")+")"}); 
}, 
hex:function(value){ 
if(/^#/.test(value)){ 
value = value.replace('#', ''); 
return "#" + (value.length == 3 ? value.replace(/^(\w)(\w)(\w)$/, '$1$1$2$2$3$3') : value); 
} 
return value; 
} 
} 
window.onload = function(){ 
new Gradient("text1",{width:800,height:100,type:1,"color-stop":["0,red","16,orange","32,yellow","48,green","64,blue","80,indigo","100,violet"]}) 
new Gradient("text2",{width:800,height:100,type:0,"color-stop":["0,red","16,orange","32,yellow","48,green","64,blue","80,indigo","100,violet"]}) 
} 
</script> 
<div id="text1" class="gradient">javascript线性渐变 by 司徒正美 实现多重水平渐变效果</div>

<div id="text2" class="gradient">javascript线性渐变 by 司徒正美 实现多重垂直渐变效果</div>

[Ctrl+A 全选注:如需引入外部Js需刷新才能执行]

javascript 线性渐变二

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