Center MB zoom circles in and out

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forked from Igathi's block: MB zoom circles in and out

<!DOCTYPE html>
<meta charset="utf-8">
<style>

.background {
  fill: none;
  pointer-events: all; 
}

.feature {
  fill: #ccc;
  cursor: pointer;
}

.selected {
  fill: #c1c1c1;
}
  
</style>
<body>
<script src="https://d3js.org/d3.v4.min.js"></script>
  
<script>
// zoom in with image positioned at the center 
// irrespective of their location and size
// Aug 14, 2019  
  
var  active = d3.select(null);
var objh = 20;    
var width = window.innerWidth;
var height = window.innerHeight;

var svg = d3.select("body").append("svg")
     
 svg.attr("width", width)
    .attr("height", height)
    .on("click", stopped, true);
 
 svg.append("rect")
    .attr("class", "background")
    .attr("width", width)
    .attr("height", height)
		.style("fill", "white")
		.style("stroke", "black")
    .on("click", reset);
  
var g = svg.append("g");

svg.call(zoom) // delete this line to disable free zooming
   .call(zoom.transform, initialTransform);

//	active.attr("class", "selected")  
//  scale = Math.max(1, Math.min(height/objh/2.05, 0.9 / Math.max(dx / width, dy / height)))
  
  scale = height/dr/2.05  // Same zoom level to all objects 
  translate = [width / 2 - scale * x, height / 2 - scale * y];
    
//  console.log("width");
  
  var transform = d3.zoomIdentity
    .translate(translate[0], translate[1])
    .scale(scale);

svg.transition()
     .duration(1000)
     .call(zoom.transform, transform);

d3.select(this).style("fill", "black");
}

function reset() {
//  d3.select(this).style("fill", "blue");
  active.classed("active", false);
  active = d3.select(null);

svg.transition()
      .duration(750)
      .call(zoom.transform, initialTransform);
}

function zoomed() {
  var transform = d3.event.transform;

g.style("stroke-width", 1.5 / transform.k + "px");
  g.attr("transform", transform);
}

// If the drag behavior prevents the default click,
// also stop propagation so we don’t click-to-zoom.
function stopped() {
  if (d3.event.defaultPrevented) d3.event.stopPropagation();
}

</script>

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