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D3.js zoom.scaleBy() Function

  • Last Updated : 01 Sep, 2020
Geek Week

The zoom.scaleBy() Function in D3.js is used to scale the current zoom transform of the selected elements by k. The reference point p does move.

Syntax:

zoom.scaleBy(selection, k[, p])

Parameters: This function accepts three parameters as mentioned above and described below:

  • selection: This parameter can be selection or transition.
  • k: This parameter is a scale factor, specified either as numbers or as functions
  • p: The value of p is not specified, it defaults value is the center of the viewport extent.

Return Value: This function returns the zoom behavior.

Below programs illustrate the zoom.scaleBy() function in D3.js



Example 1:

HTML




<!DOCTYPE html> 
<html
  
<head
    <meta charset="utf-8">
      
    <script src=
        "https://d3js.org/d3.v4.min.js"
    </script>
      
    <style>
        circle {
          opacity: 0.7;
        }
        g.zoom-controls {
            cursor: pointer;
            pointer-events: all;
        }
        g.zoom-controls rect {
            fill: white;
            stroke: #596877;
            stroke-width: 1;
        }
        g.zoom-controls line {
            stroke: #596877;
            stroke-width: 2;
        }
    </style>
</head
    
<body
    <center>
        <h1 style="color: green;"
            Geeksforgeeks 
        </h1
      
        <h3>
            D3.js | zoom.scaleBy() Function
        </h3>
          
        <svg>
  
            <g class="zoom-controls" transform="translate(10, 10)">
  
                <g id="zoom-in" transform="translate(0, 0)">
  
                    <rect width="30" height="30"></rect>
  
                    <line x1="5" y1="15" x2="25" y2="15"></line>
  
                    <line x1="15" y1="5" x2="15" y2="25"></line>
                </g>
  
                <g id="zoom-out" transform="translate(30, 0)">
  
                    <rect width="30" height="30"></rect>
  
                    <line x1="5" y1="15" x2="25" y2="15"></line>
  
                </g>
  
            </g>
  
        </svg>
          
        <script>
            var radius = 10;
            var svg = d3.select('svg');  
            var dimension = document.body.getBoundingClientRect();
              
            var data = d3.range(0, 25).map(function() {
                return {
                x: getRandom(radius, dimension.width - radius),
                y: getRandom(radius, dimension.height - radius)
              }
            });
              
            var zoom = d3.zoom()
                .on('zoom', function() {
                canvas.attr('transform', d3.event.transform);
            });
              
            var canvas = svg
                .attr('width', dimension.width)
                .attr('height', dimension.height)
                .call(zoom)
                .insert('g', ':first-child');
  
            canvas.selectAll('circle')
                .data(data)
                .enter()
                .append('circle')
                .attr('r', radius)
                .attr('cx', function(d) {
                return d.x;
                }).attr('cy', function(d) {
                return d.y;
                }).style('fill', function() {
                return d3.schemeCategory10[getRandom(0, 9)]
                });
              
            d3.select('#zoom-in').on('click', function() {
                // Smooth zooming
                zoom.scaleBy(svg.transition().duration(750), 1.3);
            });
              
            d3.select('#zoom-out').on('click', function() {
                // Ordinal zooming
                zoom.scaleBy(svg, 1 / 1.3);
            });
              
            function getRandom(min, max) {
                min = Math.ceil(min);
                max = Math.floor(max);
                return Math.floor(Math.random() * (max - min + 1)) + min;
            }
        </script
    </center>
</body
  
</html>

Output:

Example 2:

HTML




<!DOCTYPE html> 
<html
<head
    <meta charset="utf-8">
      
    <script src=
        "https://d3js.org/d3.v5.js">
    </script>
      
</head
    
<body
    <center>
        <h1 style="color: green;"
            Geeksforgeeks 
        </h1
      
        <h3>D3.js | zoom.scaleBy() Function</h3>
          
        <svg height="100px" width="100px"></svg>
          
        <script>
            const zoom_action = () => g.attr("transform", d3.event.transform);
  
            // Create the zoom handler
            const zoom = d3.zoom()
                    .on("zoom", zoom_action);
              
            // Get SVG element and apply zoom behaviour
            var svg = d3
              .select("svg")
              .call(zoom);
              
            // Create Group that will be zoomed
            var g = svg.append("g");
              
            // Create circle
            g.append("circle")
              .attr("cx",0)
              .attr("cy",0)
              .attr("r", 5)
              .style("fill","green");
              
            // Use of zoom.scaleBy Function
            zoom.scaleBy(svg, 5);
            zoom.translateBy(svg, 50, 50);
  
        </script
    </center>
</body
  
</html>

Output:

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