CanvasRenderingContext2D.currentTransform

The CanvasRenderingContext2D.currentTransform property of the Canvas 2D API returns or sets an SVGMatrix object for the current transformation matrix.

Syntax

ctx.currentTransform [= value];

value

An SVGMatrix object to use as the current transformation matrix.

Examples

Using the currentTransform method

This is just a simple code snippet that uses the currentTransform property to set a transformation matrix.

HTML

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

JavaScript

var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");

var matrix = ctx.currentTransform;
matrix.a = 1;
matrix.b = 1;
matrix.c = 0;
matrix.d = 1;
matrix.e = 0;
matrix.f = 0;
ctx.currentTransform = matrix;
ctx.fillRect(0,0,100,100);

Edit the code below and see your changes update live in the canvas (make sure to use a browser that supports this feature — see the compatibility table):

<canvas id="canvas" width="400" height="200" class="playable-canvas"></canvas>
<div class="playable-buttons">
  <input id="edit" type="button" value="Edit" />
  <input id="reset" type="button" value="Reset" />
</div>
<textarea id="code" class="playable-code" style="height:150px">
var matrix = ctx.currentTransform;
matrix.a = 1;
matrix.b = 1;
matrix.c = 0;
matrix.d = 1;
matrix.e = 0;
matrix.f = 0;
ctx.currentTransform = matrix;
ctx.fillRect(0,0,100,100);</textarea>

var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var textarea = document.getElementById("code");
var reset = document.getElementById("reset");
var edit = document.getElementById("edit");
var code = textarea.value;

function drawCanvas() {
  ctx.clearRect(0, 0, canvas.width, canvas.height);
  eval(textarea.value);
}

reset.addEventListener("click", function() {
  textarea.value = code;
  drawCanvas();
});

edit.addEventListener("click", function() {
  textarea.focus();
})

textarea.addEventListener("input", drawCanvas);
window.addEventListener("load", drawCanvas);

Specifications

Browser compatibility

[1] This feature is deactivated by default. Enable the ExperimentalCanvasFeatures flag to test it.

[2] See bug 928150. Gecko also supports the experimental and prefixed properties mozCurrentTransform and mozCurrentTransformInverse which set or get the current (inverse) transformation matrix.

See also

• The interface defining it, CanvasPattern
• SVGMatrix