Web/API/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 StandardThe definition of 'CanvasRenderingContext2D.scale' in that specification.	Living Standard

Browser compatibility

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

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	Safari on iOS	Samsung Internet
scale	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

Legend

Full support  

Full support

See also

• The interface defining this method: CanvasRenderingContext2D

CanvasRenderingContext2D.scale() by Mozilla Contributors is licensed under CC-BY-SA 2.5.