HTMLCanvasElement

The HTMLCanvasElement interface provides properties and methods for manipulating the layout and presentation of canvas elements. The HTMLCanvasElement interface also inherits the properties and methods of the HTMLElement interface.

Properties

Inherits properties from its parent, HTMLElement.

HTMLCanvasElement.height

Is a positive integer reflecting the height HTML attribute of the <canvas> element interpreted in CSS pixels. When the attribute is not specified, or if it is set to an invalid value, like a negative, the default value of 150 is used.

HTMLCanvasElement.mozOpaque

Is a Boolean reflecting the moz-opaque HTML attribute of the <canvas> element. It lets the canvas know whether or not translucency will be a factor. If the canvas knows there's no translucency, painting performance can be optimized.

HTMLCanvasElement.width

Is a positive integer reflecting the width HTML attribute of the <canvas> element interpreted in CSS pixels. When the attribute is not specified, or if it is set to an invalid value, like a negative, the default value of 300 is used.

HTMLCanvasElement.mozPrintCallback

Is a function that is Initially null, Web content can set this to a JavaScript function that will be called if the page is printed. This function can then redraw the canvas at a higher resolution that is suitable for the printer being used. See this blog post.

Methods

Inherits methods from its parent, HTMLElement.

HTMLCanvasElement.captureStream()

Returns a CanvasCaptureMediaStream that is a real-time video capture of the surface of the canvas.

HTMLCanvasElement.getContext()

Returns a drawing context on the canvas, or null if the context ID is not supported. A drawing context lets you draw on the canvas. Calling getContext with "2d" returns a CanvasRenderingContext2D object, whereas calling it with "experimental-webgl" (or "webgl") returns a WebGLRenderingContext object. This context is only available on browsers that implement WebGL.

HTMLCanvasElement.toDataURL()

Returns a data-URL containing a representation of the image in the format specified by the type parameter (defaults to png). The returned image is in a resolution of 96dpi.

HTMLCanvasElement.toBlob()

Creates a Blob object representing the image contained in the canvas; this file may be cached on the disk or stored in memory at the discretion of the user agent.

HTMLCanvasElement.transferControlToOffscreen()

Transfers control to an OffscreenCanvas object, either on the main thread or on a worker.

HTMLCanvasElement.mozGetAsFile()

Returns a File object representing the image contained in the canvas; this file is a memory-based file, with the specified name. If type is not specified, the image type is image/png.

Specifications

Specification	Status	Comment
Media Capture from DOM Elements The definition of 'HTMLCanvasElement' in that specification.	Editor's Draft	Adds the method captureStream().
WHATWG HTML Living Standard The definition of 'HTMLCanvasElement' in that specification.	Living Standard	The method getContext() now returns a RenderingContext rather than an opaque object. The methods probablySupportsContext(), setContext() and transferControlToProxy()have been added.
HTML5.1 The definition of 'HTMLCanvasElement' in that specification.	Recommendation
HTML5 The definition of 'HTMLCanvasElement' in that specification.	Recommendation	Initial definition.

Browser compatibility

[1] Opera Mini 5.0 and later has partial support.

[2] Support for the third parameter, has been added in Gecko 25 only: when used with the "image/jpeg" type, this argument specifies the image quality.

[3] This feature is behind a feature preference setting. In about:config, set gfx.offscreencanvas.enabled to true.

See also

• HTML element implementing this interface: <canvas>.