OffscreenCanvas

new OffscreenCanvas(width, height): OffscreenCanvas

Parameters

Parameter	Type	Description
`width`	`number`	The width of the offscreen canvas.
`height`	`number`	The height of the offscreen canvas.

Properties

Property	Type	Default value	Description
`height`	`number`	`undefined`	Specifies the height (in pixels) of the canvas. See https://developer.mozilla.org/docs/Web/API/OffscreenCanvas/height
`oncontextlost`	`null`	`null`	MDN Reference
`oncontextrestored`	`null`	`null`	MDN Reference
`width`	`number`	`undefined`	Specifies the width (in pixels) of the canvas. See https://developer.mozilla.org/docs/Web/API/OffscreenCanvas/height

Methods

addEventListener()

addEventListener(type, callback, options?): void

Appends an event listener for events whose type attribute value is type. The callback argument sets the callback that will be invoked when the event is dispatched.

The options argument sets listener-specific options. For compatibility this can be a boolean, in which case the method behaves exactly as if the value was specified as options's capture.

When set to true, options's capture prevents callback from being invoked when the event's eventPhase attribute value is BUBBLING_PHASE. When false (or not present), callback will not be invoked when event's eventPhase attribute value is CAPTURING_PHASE. Either way, callback will be invoked if event's eventPhase attribute value is AT_TARGET.

When set to true, options's passive indicates that the callback will not cancel the event by invoking preventDefault(). This is used to enable performance optimizations described in § 2.8 Observing event listeners.

When set to true, options's once indicates that the callback will only be invoked once after which the event listener will be removed.

If an AbortSignal is passed for options's signal, then the event listener will be removed when signal is aborted.

The event listener is appended to target's event listener list and is not appended if it has the same type, callback, and capture.

Parameters

Parameter	Type
`type`	`string`
`callback`	`null` \| `EventListenerOrEventListenerObject`<`any`>
`options`?	`boolean` \| `AddEventListenerOptions`

Returns

void

Implementation of

Omit.addEventListener

Inherited from

EventTarget.addEventListener

See

https://developer.mozilla.org/docs/Web/API/EventTarget/addEventListener

convertToBlob()

convertToBlob(options?): Promise<Blob>

Returns a promise that will fulfill with a new Blob object representing a file containing the image in the OffscreenCanvas object.

The argument, if provided, is a dictionary that controls the encoding options of the image file to be created. The type field specifies the file format and has a default value of "image/png"; that type is also used if the requested type isn't supported. If the image format supports variable quality (such as "image/jpeg"), then the quality field is a number in the range 0.0 to 1.0 inclusive indicating the desired quality level for the resulting image.

MDN Reference

Parameters

Parameter	Type
`options`?	`ImageEncodeOptions`

Returns

Promise<Blob>

Implementation of

Omit.convertToBlob

dispatchEvent()

dispatchEvent(event): boolean

Dispatches a synthetic event event to target and returns true if either event's cancelable attribute value is false or its preventDefault() method was not invoked, and false otherwise.