d3.js geoWinkel3()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geoWinkel3()函数用于绘制Winkel tripel投影，这是对世界Map的折衷修改后的方位角投影。它是Aitoff和等距圆柱投影的投影坐标的算术平均值。已知该投影在small-scale映射的折衷投影中具有最低的平均比例和面积失真之一。

用法:

d3.geoWinkel3()

参数：此方法不接受任何参数。

返回值：此方法根据给定的JSON数据创建并返回Winkel3投影。

范例1：以下示例对Winkel3进行投影，其中心为(0,0)，旋转为0。

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"); 
  
        // Winkel3 projection 
        // Center(0,0) with 0 rotation 
        var gfg = d3.geoWinkel3() 
            .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", "SlateBlue") 
                    .attr("d", d3.geoPath() 
                        .projection(gfg) 
                    ) 
                    .style("stroke", "#ffff") 
        }); 
    </script> 
</body>  
  
</html>

输出：

Winkel3世界的投影，无旋转且以(0,0)为中心

范例2：以下示例在自定义中心和旋转之后使Winkel3投影世界

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:500px; height:600px;">  
        <svg width="500" height="450">  
        </svg>  
    </div>  
      
    <script> 
        var svg = d3.select("svg"), 
            width = +svg.attr("width"), 
            height = +svg.attr("height"); 
  
        // Winkel3  projection 
        // Center(-10,0) and -90 degree 
        // rotation w.r.t Y axis 
        var gfg = d3.geoWinkel3() 
            .scale(width / 1.3 / 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", "SaddleBrown") 
                    .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 geoWinkel3() 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。