javascript线性渐变2

原创|其它|编辑：郝浩|2009-10-14 11:20:43.000|阅读 346 次

概述：javascript在处理图像的能力其实是不弱的，可惜浏览器大战连累了它，这还不算，Adobe 收购Macromedia更让SVG处于怠工状态。作为新力军，苹果为我们带来了canvas标签。

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。

//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); 
}

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。

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：

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

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。

   
new Gradient("gradient",{width:800,height:100,type:0,"color-stop":["0,red", 
"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> <br /> <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>

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