mbostock/.block

## .block
license: gpl-3.0
redirect: https://observablehq.com/@d3/zoom

## README.md

      
        
                
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              README.md
            
          
        
      
      
    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.

  

  

## index.html
<!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(2000).map(phyllotaxis(10));

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", 2.5);

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));

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>

## preview.png

      
        
                
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              preview.png
            
          
        
      
    
    

        
            
        
    

  

## thumbnail.png

      
        
                
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              thumbnail.png
	<!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(2000).map(phyllotaxis(10));

	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", 2.5);

	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));

	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>