Pan & Zoom III# endorse

This example demonstrates using d3-zoom to pan and zoom an SVG element by applying an SVG transform using transform.toString. The zoom behavior is applied to an invisible rect overlaying the SVG element; this ensures that it receives input, and that the pointer coordinates are not affected by the zoom behavior’s transform.

forked from mbostock's block: Pan & Zoom III

<!DOCTYPE html>
<meta charset="utf-8">
<svg width="960" height="500"></svg>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script>

var svg = d3.select("svg"),
    width = +svg.attr("width"),
    height = +svg.attr("height");

var points = d3.range(200).map(phyllotaxis(10));
// d3.range(x) 决定有x个点
  
var g = svg.append("g");

g.selectAll("circle")
    .data(points)
  .enter().append("circle")
    .attr("cx", function(d) { return d[0]; })
    .attr("cy", function(d) { return d[1]; })
    .attr("r", 2.2);

svg.append("rect")
    .attr("width", width)
    .attr("height", height)
    .style("fill", "none")
    .style("pointer-events", "all")
    .call(d3.zoom()
        .scaleExtent([1 / 2, 4])
        .on("zoom", zoomed));
//The pointer-events CSS property specifies under what circumstances (if any) a particular graphic element can become the target of mouse events.
  
//all: SVG only. The element can only be the target of a mouse event when the pointer is over the interior (i.e., fill) or the perimeter (i.e., stroke) of the element. The values of the fill, stroke and visibility properties do not affect event processing.  
  
  
function zoomed() {
  g.attr("transform", d3.event.transform);
}

function phyllotaxis(radius) {
  var theta = Math.PI * (3 - Math.sqrt(5));
  return function(i) {
    var r = radius * Math.sqrt(i), a = theta * i;
    return [
      width / 2 + r * Math.cos(a),
      height / 2 + r * Math.sin(a)
    ];
  };
}

</script>

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