[Edit]

JavaScript - scale drawing on canvas

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Created by:

Vanessa-Drake

718

In this article, we would like to show you how to

Quick solution:

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var canvas = document.querySelector('#canvas');
var context = canvas.getContext('2d');
context.scale(0.5, 1.5); // scale(x, y)

Practical example

Edit

In this example, we use scale() method to add a scaling transformation to the canvas2 units horizontally and vertically.

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<!doctype html>
<html>
<head>
  <style>
    
    canvas { border: 1px solid gray; }
    
  </style>
</head>
<body>
  <div>Original:</div>
  <canvas id="canvas1" width="200" height="200"></canvas>
  <br>
  <div>Scaled:</div>
  <canvas id="canvas2" width="200" height="200"></canvas>
  <script>
​
    var canvas1 = document.querySelector('#canvas1');
    var canvas2 = document.querySelector('#canvas2');
    
    var context1 = canvas1.getContext('2d');
    var context2 = canvas2.getContext('2d');
​
    // -------------------------------------------------------------
    // drawSquare source: https://dirask.com/posts/DKL5gp
​
    function drawSquare(context, x, y, side) {
        context.strokeStyle = 'red';
        context.beginPath();
        context.rect(x, y, side, side); // rect(x, y, width, height)
        context.stroke();
    }
​
    // -------------------------------------------------------------
​
    drawSquare(context1, 30, 30, 100);
    
    // scale canvas x-axis * 0.5 and y-axis * 1.2
    context2.scale(0.5, 1.2);
​
    drawSquare(context2, 30, 30, 100);
    
  </script>
</body>
</html>