CanvasRenderingContext2D.globalCompositeOperation

The CanvasRenderingContext2D.globalCompositeOperation property of the Canvas 2D API sets the type of compositing operation to apply when drawing new shapes.

See also Compositing and clipping in the Canvas Tutorial.

A string identifying which of the compositing or blending mode operations to use.

This example uses the globalCompositeOperation property to draw two rectangles that exclude themselves where they overlap.

HTML

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

JavaScript

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

ctx.globalCompositeOperation = 'xor';

ctx.fillStyle = 'blue';
ctx.fillRect(10, 10, 100, 100);

ctx.fillStyle = 'red';
ctx.fillRect(50, 50, 100, 100);

Result

• In WebKit- and Blink-based Browsers, a non-standard and deprecated method ctx.setCompositeOperation() is implemented besides this property.
• Support for "plus-darker" and "darker" were removed in Chrome 48. Developers looking for a replacement should use "darken".

• An early Canvas specification draft specified the value "darker". However, Firefox removed support for "darker" in version 4 (bug 571532). See also this blog post that suggests using "difference" as a way to achieve a similar affect to "darker".

• The interface defining this property: CanvasRenderingContext2D
• CanvasRenderingContext2D.globalAlpha