d3.js geoMercator()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geoMercator()函數用於繪製球形墨卡托投影。

用法:

d3.geoMercator()

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Mercator投影。

範例1：下麵的示例繪製中心為(0，0)且旋轉為0的世界的Mercator投影。

<!DOCTYPE html> 
<html lang="en"> 
    <head> 
        <meta charset="UTF-8" /> 
        <meta
            name="viewport"
            content="width=device-width,  
                initial-scale=1.0" 
        /> 
    </head> 
  
    <body> 
        <div style="width:700px; height:500px;"> 
            <center> 
                <h3 style="color:black;"></h3> 
            </center> 
  
            <svg width="600" 
                 height="450"></svg> 
        </div> 
        <script src="https://d3js.org/d3.v4.js"></script> 
        <script src= 
                "https://d3js.org/d3-geo-projection.v2.min.js"> 
      </script> 
        <script> 
            var svg = d3.select("svg"), 
                width = +svg.attr("width"), 
                height = +svg.attr("height"); 
  
            // Mercator projection 
            // Center(0, 0) with 0 rotation 
            var gfg = d3 
                .geoMercator() 
                .scale(width / 2.5 / 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) { 
                // 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>

輸出：

墨卡托投影世界，無旋轉且以(0，0)為中心

範例2：以下示例在更改中心和旋轉後繪製墨卡托世界投影。

<!DOCTYPE html> 
<html lang="en"> 
    <head> 
        <meta charset="UTF-8" /> 
        <meta
            name="viewport"
            content="width=device-width,  
                initial-scale=1.0" 
        /> 
    </head> 
  
    <body> 
        <div style="width:700px; height:600px;"> 
            <center> 
                <h3 style="color:black;"></h3> 
            </center> 
  
            <svg width="500" height="450"></svg> 
        </div> 
        <script src="https://d3js.org/d3.v4.js"></script> 
        <script src= 
             "https://d3js.org/d3-geo-projection.v2.min.js"> 
      </script> 
        <script> 
            var svg = d3.select("svg"), 
                width = +svg.attr("width"), 
                height = +svg.attr("height"); 
  
            // Mercator  projection 
 // Center(20, 20) and 90 degree rotation w.r.t Y axis 
            var gfg = d3 
                .geoMercator() 
                .scale(width / 2.5 / Math.PI) 
                .rotate([90, 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", "Turquoise").attr( 
                  "d", d3.geoPath().projection(gfg)).style( 
                  "stroke", "#ffff"); 
            }); 
        </script> 
    </body> 
</html>

輸出：

墨卡托投影，Y軸旋轉90度，並以(20，20)為中心

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 geoMercator() 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。