README.md

## README.md

      
        

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              README.md
            
          
        
      
    
  
    A variation of programmatic zoom where buttons can be used to zoom-in or zoom-out around the current center of the viewport.

  

  

## index.html
<!DOCTYPE html>
<meta charset="utf-8">
<title>Zoom + Pan</title>
<style>

body {
  position: relative;
  width: 960px;
}

svg {
  font: 10px sans-serif;
  shape-rendering: crispEdges;
}

rect {
  fill: #ddd;
}

.axis path,
.axis line {
  fill: none;
  stroke: #fff;
}

.buttons {
  position: absolute;
  right: 30px;
  top: 30px;
}

</style>
<div class="buttons">
  <button data-zoom="+1">Zoom In</button>
  <button data-zoom="-1">Zoom Out</button>
</div>
<script src="http://d3js.org/d3.v3.min.js"></script>
<script>

var margin = {top: 20, right: 20, bottom: 30, left: 40},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

var x = d3.scale.linear()
    .domain([-width / 2, width / 2])
    .range([0, width]);

var y = d3.scale.linear()
    .domain([-height / 2, height / 2])
    .range([height, 0]);

var xAxis = d3.svg.axis()
    .scale(x)
    .orient("bottom")
    .tickSize(-height);

var yAxis = d3.svg.axis()
    .scale(y)
    .orient("left")
    .ticks(5)
    .tickSize(-width);

var zoom = d3.behavior.zoom()
    .x(x)
    .y(y)
    .scaleExtent([1, 10])
    .center([width / 2, height / 2])
    .size([width, height])
    .on("zoom", zoomed);

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 + ")")
    .call(zoom);

svg.append("rect")
    .attr("width", width)
    .attr("height", height);

svg.append("g")
    .attr("class", "x axis")
    .attr("transform", "translate(0," + height + ")")
    .call(xAxis);

svg.append("g")
    .attr("class", "y axis")
    .call(yAxis);

d3.selectAll("button[data-zoom]")
    .on("click", clicked);

function zoomed() {
  svg.select(".x.axis").call(xAxis);
  svg.select(".y.axis").call(yAxis);
}

function clicked() {
  svg.call(zoom.event); // https://github.com/mbostock/d3/issues/2387

  // Record the coordinates (in data space) of the center (in screen space).
  var center0 = zoom.center(), translate0 = zoom.translate(), coordinates0 = coordinates(center0);
  zoom.scale(zoom.scale() * Math.pow(2, +this.getAttribute("data-zoom")));

  // Translate back to the center.
  var center1 = point(coordinates0);
  zoom.translate([translate0[0] + center0[0] - center1[0], translate0[1] + center0[1] - center1[1]]);

  svg.transition().duration(750).call(zoom.event);
}

function coordinates(point) {
  var scale = zoom.scale(), translate = zoom.translate();
  return [(point[0] - translate[0]) / scale, (point[1] - translate[1]) / scale];
}

function point(coordinates) {
  var scale = zoom.scale(), translate = zoom.translate();
  return [coordinates[0] * scale + translate[0], coordinates[1] * scale + translate[1]];
}

</script>

## thumbnail.png

      
        

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              thumbnail.png