d3.js geoConicEqualArea()用法及代码示例

d3.js中的geoConicEqualArea()函数用于从给定的geojson数据绘制Albers的圆锥equal-area投影。

用法:

d3.geoConicEqualArea()

参数：此方法不接受任何参数。

返回值：此方法返回圆锥equal-area投影。

范例1：以下示例绘制了一个圆锥形的equal-area投影，该投影的中心为(0，0)，旋转为0度。

HTML

<!DOCTYPE html> 
<html> 
  
<head> 
    <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:500px;"> 
        <svg width="600" height="450"></svg> 
    </div> 
      
    <script> 
        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") 
            }); 
    </script> 
</body> 
  
</html>

输出：

范例2：以下示例绘制了一个圆锥形的equal-area投影，该投影的中心为(-10，0)，相对于y轴旋转90度。

HTML

<!DOCTYPE html> 
<html> 
  
<head> 
    <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;"> 
        <svg width="500" height="450"></svg> 
    </div> 
      
    <script> 
        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") 
            }); 
    </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 geoConicEqualArea() 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。