D3.js geoConicEqualArea()函数

d3.js 中的geoConicEqualArea ()函数用于从给定的 geojson 数据中绘制Albers 的圆锥等面积投影。

句法：

d3.geoConicEqualArea()

参数：此方法不接受任何参数。

返回值：此方法返回圆锥等面积投影。

示例 1：以下示例以 (0, 0) 为中心绘制世界的圆锥等面积投影，旋转 0 度。

HTML

  

    
    
    
    

  

    
        
    
      
    
        var svg = d3.select("svg"),
            width = +svg.attr("width"),
            height = +svg.attr("height");
  
        // ConicEqualArea projection with
        // Center at (0, 0) with rotation
        // of 0 degrees 
        var gfg = d3.geoConicEqualArea()
            .scale(width / 1.8 / 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) {
  
                // Drawing 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")
            });
    

  

输出：

示例 2：以下示例绘制世界的圆锥等面积投影，中心位于 (-10, 0) 并相对于 y 轴旋转 90 度。

HTML

  

    
    
    
    

  

    
        
    
      
    
        var svg = d3.select("svg"),
            width = +svg.attr("width"),
            height = +svg.attr("height");
  
        // ConicEqualArea  projection
        // Center at (-10,0) and 90 degree
        // rotation w.r.t y-axis
        var gfg = d3.geoConicEqualArea()
            .scale(width / 1.8 / Math.PI)
            .rotate([90, 0])
            .center([-10, 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", "grey")
                    .attr("d", d3.geoPath()
                        .projection(gfg)
                    )
                    .style("stroke", "#ffff")
            });
    

  

输出：