d3.js geoEquirectangular()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效果，它使用可伸缩矢量图形，HTML5和级联样式表标准。

d3.js中的geoEquirectangular()函数用于绘制等角投影，这是归因于Tyre的Marinus的简单Map投影，托勒密声称是他的发明。

用法:

d3.geoEquirectangular()

参数：此方法不接受任何参数。

返回值：此方法根据给定的json数据创建一个等角投影。

范例1：以下示例对中心为(0,0)且不旋转的世界进行等角投影。

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:500px;"> 
  
        <svg width="600" height="450"> 
        </svg> 
    </div> 
  
    <script> 
        var svg = d3.select("svg"), 
            width = +svg.attr("width"), 
            height = +svg.attr("height"); 
  
        // Equirectangular  projection 
        // Center(0,0) and no rotation 
        var gfg = d3.geoEquirectangular() 
            .scale(width / 1.5 / Math.PI) 
            .rotate([0, 0]) 
            .center([0, 0]) 
            .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：

等角投影，不旋转，并以(0,0)为中心

范例2：以下示例通过更改中心和旋转来进行世界的等角投影。

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:900px;"> 
        <svg width="400" height="450"> 
        </svg> 
    </div> 
  
    <script> 
        var svg = d3.select("svg"), 
            width = +svg.attr("width"), 
            height = +svg.attr("height"); 
  
        // Equirectangular  projection 
        // Center(0,10) and 45 degree  
        // anticlock rotation 
        var gfg = d3.geoEquirectangular() 
            .scale(width / 1.5 / Math.PI) 
            .rotate([45, 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", "grey") 
                    .attr("d", d3.geoPath() 
                        .projection(gfg) 
                    ) 
                    .style("stroke", "#ffff") 
            }) 
    </script> 
</body> 
  
</html>

输出：

旋转45度anti-clock并以(0,10)为中心的等角投影

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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 geoEquirectangular() 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。