The CanvasRenderingContext2D
.setTransform()
method of the Canvas 2D API resets (overrides) the current transformation to the identity matrix, and then invokes a transformation described by the arguments of this method. This lets you scale, rotate, translate (move), and skew the context.
Note: See also the transform()
method; instead of overriding the current transform matrix, it multiplies it with a given one.
Syntax
ctx.setTransform(a, b, c, d, e, f); ctx.setTransform(matrix);
The transformation matrix is described by:
Parameters
setTransform()
has two types of parameter that it can accept. The older type consists of several parameters representing the individual components of the transformation matrix to set:
a
(m11
)- Horizontal scaling. A value of
1
results in no scaling. b
(m12
)- Vertical skewing.
c
(m21
)- Horizontal skewing.
d
(m22
)- Vertical scaling. A value of
1
results in no scaling. e
(dx
)- Horizontal translation (moving).
f
(dy
)- Vertical translation (moving).
The newer type consists of a single parameter, matrix
, representing a 2D transformation matrix to set (technically, a DOMMatrixInit
object; any object will do as long as it contains the above components as properties).
Examples
Skewing a shape
This example skews a rectangle both vertically (.2
) and horizontally (.8
). Scaling and translation remain unchanged.
HTML
<canvas id="canvas"></canvas>
JavaScript
const canvas = document.getElementById('canvas'); const ctx = canvas.getContext('2d'); ctx.setTransform(1, .2, .8, 1, 0, 0); ctx.fillRect(0, 0, 100, 100);
Result
Retrieving and passing a DOMMatrix object
In the following example, we have two <canvas>
elements. We apply a transform to the first one's context using the first type of setTransform()
and draw a square on it, then retrieve the matrix from it using CanvasRenderingContext2D.getTransform()
.
We then apply the retrieved matrix directly to the second canvas context by passing the DOMMatrix
object directly to setTransform()
(i.e. the second type), and draw a circle on it.
HTML
<canvas width="240"></canvas> <canvas width="240"></canvas>
CSS
canvas { border: 1px solid black; }
JavaScript
const canvases = document.querySelectorAll('canvas'); const ctx1 = canvases[0].getContext('2d'); const ctx2 = canvases[1].getContext('2d'); ctx1.setTransform(1, .2, .8, 1, 0, 0); ctx1.fillRect(25, 25, 50, 50); let storedTransform = ctx1.getTransform(); console.log(storedTransform); ctx2.setTransform(storedTransform); ctx2.beginPath(); ctx2.arc(50, 50, 50, 0, 2 * Math.PI); ctx2.fill();
Result
Specifications
Specification | Status | Comment |
---|---|---|
HTML Living Standard The definition of 'CanvasRenderingContext2D.setTransform' in that specification. |
Living Standard |
Browser compatibility
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
setTransform | Chrome Full support Yes | Edge Full support 12 | Firefox Full support 3 | 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 |
Accept matrix object as parameter | Chrome Full support 68 | Edge Full support 79 | Firefox Full support 70 | IE No support No | Opera Full support 55 | Safari Full support 11 | WebView Android Full support 68 | Chrome Android Full support 68 | Firefox Android No support No | Opera Android Full support 48 | Safari iOS Full support 11 | Samsung Internet Android Full support 10.0 |
Legend
- Full support
- Full support
- No support
- No support
See also
- The interface defining this method:
CanvasRenderingContext2D
CanvasRenderingContext2D.transform()