OffscreenCanvas Class

OffscreenCanvas Class
Inherits	Description
EventTarget	This represents a broader group of objects that can receive event notices.
Constructors	Description
OffscreenCanvas(w, h)	This constructs an OffscreenCanvas object with the width and height given by w and h.
Properties	Description
height	This defines the height of the OffscreenCanvas in pixels.
width	This defines the width of the OffscreenCanvas in pixels.
Methods	Description
Promise convertToBlob() Promise convertToBlob(opt)	The returns a Blob object in the image in the Canvas in the form of a Promise. The opt paramter can be a string that indicates an image format, such as "image/png", or a number between 0 and 1 to indicate the quality of the created image when performing a conversion to lossy compression.
Object getContext(type, attrib)	This gets a context for drawing to the OffscreenCanvas, which may be of the type OffscreenCanvasRenderingContext2D, WebGLRenderingContext, WebGL2RenderingContext, or ImageBitmapRenderingContext. The type is a string that describes the type of context and it can have one of these values: "2d", "webgl", "webgl2", or "bitmaprenderer". The attrib paramter is an object with properties corresponding to the context type. For example, we might have { alpha: .5} for a "2d" context or {alpha: .75, depth: true, stencil: false, antialias: true, premultipliedAlpha: false, preserveDrawingBuffer: true, failIfMajorPerformanceCaveat: true} for a "webgl" context.
ImageBitmap transferToImageBitmap()	This creates an ImageBitmap of the most recently rendered image. To preserve resources, this ImageBitmap should be closed() or consumed by passing it to a transferFromImageBitmap() method of an ImageBitmapRenderingContext.