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May 16, 2016 pm 06:44 PM

javascript linear gradient

Let’s start with IE, which is the largest user group. If this part cannot be developed, it can basically be said that there is no need to do it. Although IE has a Gradient filter, its implementation is very weak compared to other browsers. It does not have multiple gradients (stop-color), cannot implement angle gradients, and often fails. My idea is this, if there is a DIV with text, to achieve multiple linear gradients, we must first take out the text inside it, and then put several DIVs in it, as many as there are multiple ones, and then gradient them . If it's a vertical gradient, it's easy to do. You don't have to do anything, just set its filter and height. If it's horizontal, make it float or position it absolutely, put it in place, and set its filter and width. But gradient filters actually fail after being floated or positioned, which is unheard of when using transparent filters. There is no other way, so I sacrifice the ancient artifact table. But when setting the length and width, it is not useful to use style to set it. You must use DOM attributes. The gradient is responsible for its td element. In order to remove the space between the table element and the td element, and between the td element and its content, we also have to use cellPadding and cellSpacing.

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]

Safari, chrome and opera are planned All implemented using SVG. In order to reduce the length of the function, two auxiliary functions were specially created.

Copy code

The code is as follows:

 
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;ivar 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 Use its private properties:

Copy code

The code is as follows:

 
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;ivar 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。

<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"]}) 

<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]

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