d3.js geoEckert3()用法及代碼示例

D3.js是一個JavaScript庫，用於在Web瀏覽器中生成動態的交互式數據可視化。它利用可伸縮矢量圖形，HTML5和級聯樣式表標準。 d3.js中的geoEckert3()函數用於繪製Eckert III投影，該投影是既不是保形也不是等麵積的偽圓柱投影。此投影由Max Eckert於1906年提出，主要用於世界Map。

用法:

d3.geoEckert3()

參數：此方法不接受任何參數。

返回：此方法根據給定的JSON數據創建Eckert3投影。

範例1：以下示例對Eckert3進行投影，該投影的中心為(0，0)，並且沒有旋轉。

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>

輸出：

範例2：在下麵的示例中，我們將製作Eckert3投影，其中心為(20，20)，並且相對於y軸逆時針旋轉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>

輸出：

相關用法

注：本文由純淨天空篩選整理自jana_sayantan大神的英文原創作品 D3.js geoEckert3() Function。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。