CanvasRenderingContext2D.rotate()

The CanvasRenderingContext2D.rotate() method of the Canvas 2D API adds a rotation to the transformation matrix. The angle argument represents a clockwise rotation angle and is expressed in radians.

Syntax

void ctx.rotate(angle);

Parameters

angle

The angle to rotate clockwise in radians. You can use degree * Math.PI / 180 if you want to calculate from a degree value.

The rotation center point is always the canvas origin. To change the center point, we will need to move the canvas by using the translate() method.

Examples

Using the rotate method

This is just a simple code snippet which uses the rotate method.

HTML

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

JavaScript

var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
ctx.rotate(45 * Math.PI / 180);
ctx.fillRect(70, 0, 100, 30);
// reset current transformation matrix to the identity matrix
ctx.setTransform(1, 0, 0, 1, 0, 0);

Edit the code below and see your changes update live in the canvas:

<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">
ctx.rotate(45 * Math.PI / 180);
ctx.fillRect(70,0,100,30);
ctx.setTransform(1, 0, 0, 1, 0, 0);</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

See also

• The interface defining it, CanvasRenderingContext2D