d3.js geoEckert3()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geoEckert3()函数用于绘制Eckert III投影，该投影是既不是保形也不是等面积的伪圆柱投影。此投影由Max Eckert于1906年提出，主要用于世界Map。

用法:

d3.geoEckert3()

参数：此方法不接受任何参数。

返回：此方法根据给定的JSON数据创建Eckert3投影。

范例1：以下示例对Eckert3进行投影，该投影的中心为(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:black"> 
                Eckert III 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"); 
  
        // geoEckert III  projection 
        // Center(0, 0) and no rotation 
        var gfg = d3.geoEckert3() 
            .scale(width / 1.5 / Math.PI) 
            .rotate([-10, 0]) 
            .center([0, -10]) 
            .translate([width / 2, height / 2]) 
  
        // Loading the json data 
        // Used json file stored at  
        // https://raw.githubusercontent.com/janasayantan 
        // datageojson/master/world.json 
        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：在下面的示例中，我们将制作Eckert3投影，其中心为(20，20)，并且相对于y轴逆时针旋转30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:black"> 
                Eckert III Projection of World 
            </h3> 
  
        </center> 
  
        <svg width="700" height="400"> 
        </svg> 
    </div> 
  
    <script> 
        var svg = d3.select("svg"), 
            width = +svg.attr("width"), 
            height = +svg.attr("height"); 
  
        // geoEckert III  projection 
        // Center(20, 20) and  rotating 30  
        // degree anti-clockwise 
        var gfg = d3.geoEckert3() 
            .scale(width / 1.5 / Math.PI) 
            .rotate([-30, 0]) 
            .center([20, 20]) 
            .translate([width / 2, height / 2]) 
  
        // Loading the json data 
        // Used json file stored at  
        // https://raw.githubusercontent.com/janasayantan 
        // datageojson/master/world.json 
        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 geoEckert3() 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。