D3.js geoBromley() Function

Last Updated : 18 Sep, 2020

D3.js is a JavaScript library for producing dynamic, interactive data visualizations in web browsers. It makes use of Scalable Vector Graphics, HTML5, and Cascading Style Sheets standards.
The geoBromley() function in d3.js is used to draw the Bromley projection which is also a rescaled Mollweide projection.

Syntax:

d3.geoBromley()

Parameters: This method does not accept any parameters.

Returns Value: This method creates a Bromley projection from given json data.

Example 1: The following example makes Bromley projection of world with center at (0, 0) and no rotation.

<!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;"> 
        <center> 
            <h3 style="color:black"> 
            </h3> 
        </center> 
        <svg width="600" height="450"> 
        </svg> 
    </div> 
  
    <script> 
        var svg = d3.select("svg"), 
            width = +svg.attr("width"), 
            height = +svg.attr("height"); 
  
        // Bromley projection 
        // Center(0, 0) with 0 rotation 
        var gfg = d3.geoBromley() 
            .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 
        var myURL = "https://raw.githubusercontent.com/" 
            + "janasayantan/datageojson/master/world.json" 
  
        d3.json(myURL, function (data) { 
  
            // Draw the map 
            svg.append("g") 
                .selectAll("path") 
                .data(data.features) 
                .enter().append("path") 
                .attr("fill", "DarkGoldenRod") 
                .attr("d", d3.geoPath() 
                    .projection(gfg) 
                ) 
                .style("stroke", "#ffff") 
        }) 
    </script> 
</body> 
  
</html> 

Output:

Bromley projection with no rotation and centered at (0, 0)

Example 2: The following example makes Bromley projection of world after customizing the center and rotation.

<!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"></h3> 
    </center> 
    <svg width="700" height="400"> 
    </svg> 
    </div> 
  
    <script> 
        var svg = d3.select("svg"), 
            width = +svg.attr("width"), 
            height = +svg.attr("height"); 
  
        // Bromley  projection 
        // Center(0, 0) and 20 degree  
        // rotation w.r.t X axis 
        var gfg = d3.geoBromley() 
            .scale(width / 1.5 / Math.PI) 
            .rotate([0, 20]) 
            .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 
  
        var myURL = "https://raw.githubusercontent.com/" 
            + "janasayantan/datageojson/master/world.json" 
  
        d3.json(myURL, 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> 