Brush Minimap

Using d3-brush to create an interactive minimap.

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <script src="https://d3js.org/topojson.v2.min.js"></script>
  <style>
    body { margin: 0; position: fixed; top: 0; right: 0; bottom: 0; left: 0; }
    
    .minimap {
      fill: white;
      stroke: black;
    }
    
    .land {
      fill: green;
      fill-opacity: 0.5;
    }
    
    .minimap-land {
      fill: white;
      stroke: black;
      stroke-width: 0.5;
    }
    
    .exterior {
      fill: none;
      stroke: black;
      stroke-width: 0.5;
		}
    
    .interior {
      fill: none;
      stroke: black;
      stroke-opacity: 0.5;
      stroke-width: 0.5;
    }
    
    .border {
      fill: none;
      stroke: black;
    }
    
    g.brush > .handle {
    	display: none;
    }
    
    .overlay {
      pointer-events: none;
    }
  </style>
</head>

<body>
  <script>
		var margin = {top: 0, right: 0, bottom: 0, left: 0};
    
    var width = 960 - margin.left - margin.right,
    		height = 500 - margin.top - margin.bottom;
    
    var minimapMargin = {right: 20, bottom: 20};
    
    var minimapWidth = width / 4,
        minimapHeight = height / 4;
    
    var svg = d3.select("body").append("svg")
          .attr("width", width + margin.left + margin.right)
          .attr("height", height + margin.top + margin.bottom)
        .append("g")
          .attr("transform", "translate(" + margin.left + "," + margin.top + ")");
 
    var minimap = svg.append("g")
      .attr("transform", "translate(" + (width - minimapWidth - minimapMargin.right)  + "," +  (height - minimapHeight- minimapMargin.bottom) + ")");
    
    minimap.append("rect")
    	.attr("class", "minimap")
    	.attr("width", minimapWidth)
    	.attr("height", minimapHeight);
    
    var brush = d3.brush()
    	.extent([[0, 0], [minimapWidth, minimapHeight]])
    	.on("start brush", brushed);
        
    var projection = d3.geoEquirectangular();
    var path = d3.geoPath().projection(projection);
    
    var miniProjection = d3.geoEquirectangular();
    var miniPath = d3.geoPath().projection(miniProjection);
    
    var mapSource = "https://unpkg.com/world-atlas@1/world/110m.json"
    
    d3.json(mapSource, function(error, world) {
      if (error) throw error;
      
      var land = topojson.feature(world, world.objects.land);
      
      var exteriors = topojson.mesh(world,  world.objects.countries, function(a, b) { return a == b; });
 			var interiors = topojson.mesh(world,  world.objects.countries, function(a, b) { return a !== b; });
            
      projection.fitSize([width, height], land);
      miniProjection.fitSize([minimapWidth, minimapHeight], land);
      
      var landMap = svg.append("g")
      	.append("path")
      	.datum(land)
      	.attr("class", "land")
      	.attr("d", path);
      
      var exteriors = svg.append("g")
				.append("path")
      	.datum(exteriors)
      	.attr("class", "exterior")
      	.attr("d", path);
      
      var interiors = svg.append("g")
				.append("path")
      	.datum(interiors)
      	.attr("class", "interior")
      	.attr("d", path);
      
      minimap.raise();
      
			minimap.append("g")
      	.append("path")
      	.datum(land)
      	.attr("class", "minimap-land")
      	.attr("d", miniPath);
      
      minimap.append("g")
      	.attr("class", "brush")
      	.call(brush)
      	.call(brush.move, [[0, 0], [minimapWidth / 2, minimapHeight / 2]]);
            
    });
    
    function brushed() {
      var s = d3.event.selection,
          c0 = s[0],
          c1 = s[1];
      
      // convert to lat long
      var mpc0 = miniProjection.invert(c0);
      var mpc1 = miniProjection.invert(c1);
      
      // convert to larger pixels
      var pc0 = projection(mpc0);
      var pc1 = projection(mpc1);
      
      projection.center(mpc1);
      
      svg.select(".land").attr("d", path);
      svg.select(".interior").attr("d", path);
      svg.select(".exterior").attr("d", path);   
      
      svg.select(".land").attr("transform", "scale(2)")
      svg.select(".interior").attr("transform", "scale(2)")
      svg.select(".exterior").attr("transform", "scale(2)")
      
    }

</script>
</body>

https://d3js.org/d3.v4.min.js

https://d3js.org/topojson.v2.min.js