d3.js geoEckert2()用法及代码示例

D3.js是一个JavaScript库，用于在Web浏览器中生成动态的交互式数据可视化。它利用可伸缩矢量图形，HTML5和级联样式表标准。

d3.js中的geoEckert2()函数用于绘制Eckert II投影，该投影是equal-area伪圆柱图投影。在赤道方面，经度和纬度线的网络仅由直线组成，并且外边界具有细长六边形的独特形状。

用法:

d3.geoEckert2()

参数：此方法不接受任何参数。

返回值：此方法从给定的JSON数据创建Eckert2投影。

范例1：以下示例对Eckert2进行投影，其中心为(0,0)，并且没有旋转。

HTML

<!DOCTYPE html>  
<html lang="en">  
  
<head>  
    <meta charset="UTF-8" />  
    <meta name="viewport"
        content="width=device-width,  
                initial-scale=1.0"/> 
    <script src= 
        "https://d3js.org/d3.v4.js"> 
    </script> 
  
    <script src= 
"https://d3js.org/d3-geo-projection.v2.min.js"> 
    </script>  
</head>  
  
<body>  
    <div style="width:700px; height:600px;">  
        <center>  
            <h3 style="color:grey">  
                Eckart II Projection of World 
            </h3>   
        </center> 
  
        <svg width="700" height="550">  
        </svg>  
    </div>  
      
    <script> 
        var svg = d3.select("svg"), 
            width = +svg.attr("width"), 
            height = +svg.attr("height"); 
  
        // Eckart2  projection 
        var gfg = d3.geoEckert2() 
            .scale(width / 1.5 / Math.PI) 
            .rotate([0,0]) 
            .center([0,0]) 
            .translate([width / 2, height / 2]) 
  
        // Loading the json data 
        d3.json("https://raw.githubusercontent.com/" 
        + "janasayantan/datageojson/master/world.json", 
            function(data){ 
                // Draw the map 
                svg.append("g") 
                   .selectAll("path") 
                   .data(data.features) 
                   .enter().append("path") 
                   .attr("fill", "black") 
                   .attr("d", d3.geoPath() 
                       .projection(gfg) 
                   ).style("stroke", "#ffff") 
        }) 
    </script> 
</body>  
  
</html>

输出：

范例2：以下示例对Eckert II进行世界投影，其中心位于(0,0)，并且相对于X轴旋转45度。

HTML

<!DOCTYPE html>  
<html lang="en">  
  
<head>  
    <meta charset="UTF-8" />  
    <meta name="viewport"
        content="width=device-width,  
                initial-scale=1.0"/> 
    <script src= 
        "https://d3js.org/d3.v4.js"> 
    </script> 
    <script src= 
"https://d3js.org/d3-geo-projection.v2.min.js"> 
    </script>  
</head>  
  
<body>  
    <div style="width:700px; height:600px;">  
        <center>  
            <h3 style="color:grey">  
                Eckart II Projection of World 
            </h3>   
        </center> 
          
        <svg width="700" height="550">  
        </svg>  
    </div>  
      
    <script> 
        var svg = d3.select("svg"), 
            width = +svg.attr("width"), 
            height = +svg.attr("height"); 
  
        // Eckart2  projection 
        // Center(0,0) and rotating 45 degree 
        var gfg = d3.geoEckert2() 
            .scale(width / 1.5 / Math.PI) 
            .rotate([45,0]) 
            .center([0,0]) 
            .translate([width / 2, height / 2]) 
  
        // Loading the json data 
        d3.json("https://raw.githubusercontent.com/" 
        + "janasayantan/datageojson/master/world.json",  
            function(data){ 
                // Draw the map 
                svg.append("g") 
                   .selectAll("path") 
                   .data(data.features) 
                   .enter().append("path") 
                   .attr("fill", "black") 
                   .attr("d", d3.geoPath() 
                       .projection(gfg) 
                   ).style("stroke", "#ffff") 
        }) 
    </script> 
</body>  
  
</html>

输出：

相关用法

注：本文由纯净天空筛选整理自jana_sayantan大神的英文原创作品 D3.js geoEckert2() Function。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。