TheHTMLCanvasElement interface provides properties and methods for manipulating the layout and presentation of<canvas> elements. TheHTMLCanvasElement interface also inherits the properties and methods of theHTMLElement interface.

Instance properties

Inherits properties from its parent,HTMLElement.

HTMLCanvasElement.height

Theheight HTML attribute of the<canvas> element is a non-negativeinteger reflecting the number of logical pixels (or RGBA values) going down one column of the canvas. When the attribute is not specified, or if it is set to an invalid value, like a negative, the default value of150 is used. If no [separate] CSS height is assigned to the<canvas>, then this value will also be used as the height of the canvas in the length-unit CSS Pixel.

HTMLCanvasElement.width

Thewidth HTML attribute of the<canvas> element is a non-negativeinteger reflecting the number of logical pixels (or RGBA values) going across one row of the canvas. When the attribute is not specified, or if it is set to an invalid value, like a negative, the default value of300 is used. If no [separate] CSS width is assigned to the<canvas>, then this value will also be used as the width of the canvas in the length-unit CSS Pixel.

HTMLCanvasElement.mozOpaqueNon-standardDeprecated

A boolean value reflecting themoz-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. This is only supported in Mozilla-based browsers; use the standardizedcanvas.getContext('2d', { alpha: false }) instead.

HTMLCanvasElement.mozPrintCallbackNon-standard

Afunction that is Initially null. Web content can set this to a JavaScript function that will be called when the canvas is to be redrawn while the page is being printed. When called, the callback is passed a "printState" object that implements theMozCanvasPrintState interface. The callback can get the context to draw to from the printState object and must then call done() on it when finished. The purpose ofmozPrintCallback is to obtain a higher resolution rendering of the canvas at the resolution of the printer being used.See this blog post.

Instance methods

Inherits methods from its parent,HTMLElement.

HTMLCanvasElement.captureStream()

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

HTMLCanvasElement.getContext()

Returns a drawing context on the canvas, ornull if the context identifier is not supported, or the canvas has already been set to a different context mode.

HTMLCanvasElement.toDataURL()

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

HTMLCanvasElement.toBlob()

Creates aBlob 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 anOffscreenCanvas object, either on the main thread or on a worker.

Events

Inherits events from its parent,HTMLElement.

Listen to these events usingaddEventListener() or by assigning an event listener to theoneventname property of this interface.

contextlost

Fired if the browser detects that theCanvasRenderingContext2D context has been lost.

contextrestored

Fired if the browser successfully restores aCanvasRenderingContext2D context

webglcontextcreationerror

Fired if the user agent is unable to create aWebGLRenderingContext orWebGL2RenderingContext context.

webglcontextlost

Fired if the user agent detects that the drawing buffer associated with aWebGLRenderingContext orWebGL2RenderingContext object has been lost.

webglcontextrestored

Fired if the user agent restores the drawing buffer for aWebGLRenderingContext orWebGL2RenderingContext object.

Specifications

Browser compatibility

See also

• HTML element implementing this interface:<canvas>