CanvasRenderingContext2D.scale()

The `CanvasRenderingContext2D``.scale()` method of the Canvas 2D API adds a scaling transformation to the canvas units horizontally and/or vertically.

By default, one unit on the canvas is exactly one pixel. A scaling transformation modifies this behavior. For instance, a scaling factor of 0.5 results in a unit size of 0.5 pixels; shapes are thus drawn at half the normal size. Similarly, a scaling factor of 2.0 increases the unit size so that one unit becomes two pixels; shapes are thus drawn at twice the normal size.

Syntax

```void ctx.scale(x, y);
```

Parameters

`x`
Scaling factor in the horizontal direction. A negative value flips pixels across the vertical axis. A value of `1` results in no horizontal scaling.
`y`
Scaling factor in the vertical direction. A negative value flips pixels across the horizontal axis. A value of `1` results in no vertical scaling.

Examples

Scaling a shape

This example draws a scaled rectangle. A non-scaled rectangle is then drawn for comparison.

HTML

```<canvas id="canvas"></canvas>
```

JavaScript

The rectangle has a specified width of 8 and a height of 20. The transformation matrix scales it by 9x horizontally and by 3x vertically. Thus, its final size is a width of 72 and a height of 60.

Notice that its position on the canvas also changes. Since its specified corner is (10, 10), its rendered corner becomes (90, 30).

```const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');

// Scaled rectangle
ctx.scale(9, 3);
ctx.fillStyle = 'red';
ctx.fillRect(10, 10, 8, 20);

// Reset current transformation matrix to the identity matrix
ctx.setTransform(1, 0, 0, 1, 0, 0);

// Non-scaled rectangle
ctx.fillStyle = 'gray';
ctx.fillRect(10, 10, 8, 20);
```

Result

The scaled rectangle is red, and the non-scaled rectangle is gray.

Flipping things horizontally or vertically

You can use `scale(-1, 1)` to flip the context horizontally and `scale(1, -1)` to flip it vertically. In this example, the words "Hello world!" are flipped horizontally.

Note that the call to `fillText()` specifies a negative x coordinate. This is to adjust for the negative scaling factor: `-280 * -1` becomes `280`, and text is drawn leftwards from that point.

HTML

```<canvas id="canvas"></canvas>
```

JavaScript

```const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');

ctx.scale(-1, 1);
ctx.font = '48px serif';
ctx.fillText('Hello world!', -280, 90);
ctx.setTransform(1, 0, 0, 1, 0, 0);
```

Specifications

Specification Status Comment
HTML Living Standard
The definition of 'CanvasRenderingContext2D.scale' in that specification.
Living Standard

Browser compatibility

Update compatibility data on GitHub
Desktop Mobile Chrome Edge Firefox Internet Explorer Opera Safari Android webview Chrome for Android Firefox for Android Opera for Android Chrome Full support Yes Edge Full support 12 Firefox Full support 1.5 IE Full support Yes Opera Full support Yes Safari Full support Yes WebView Android Full support Yes Chrome Android Full support Yes Firefox Android Full support 4 Opera Android Full support Yes Safari iOS Full support Yes Samsung Internet Android Full support Yes

Full support
Full support