ImageBitmap.md

ImageBitmap

Namespace: SpawnDev.SpawnJS.JSObjects
Inheritance: SpawnJSObject -> ImageBitmap
MDN Reference: ImageBitmap
Transferable: Yes ([Transferable])

The ImageBitmap class represents a bitmap image that can be drawn to a canvas without undue latency. It provides an asynchronous and resource-efficient pathway to prepare textures for rendering in WebGL. ImageBitmap is a transferable object, meaning it can be sent between workers via postMessage with zero-copy transfer semantics. Create instances using the global createImageBitmap() factory method or OffscreenCanvas.TransferToImageBitmap().

Constructors

Signature	Description
ImageBitmap(SpawnJSObjectReference _ref)	Deserialization constructor - wraps an existing JS object reference.

Properties

Property	Type	Description
Width	uint	The width of the bitmap in CSS pixels.
Height	uint	The height of the bitmap in CSS pixels.

Methods

Method	Return Type	Description
Close()	void	Disposes of all graphical resources associated with this ImageBitmap. After calling Close(), the bitmap dimensions become 0 and the image data is no longer accessible.

Global Factory Method

ImageBitmap instances are typically created using the global createImageBitmap() method:

// Create from various image sources via SpawnJSRuntime
using var bitmap = await JS.CallAsync<ImageBitmap>("createImageBitmap", imageSource);

Supported sources include Blob, ImageData, HTMLImageElement, HTMLCanvasElement, OffscreenCanvas, HTMLVideoElement, and SVGImageElement.

Example

@inject SpawnJSRuntime JS

// Create an ImageBitmap from a Blob
using var blob = new Blob(new byte[][] { imageBytes }, new BlobOptions { Type = "image/png" });
using var bitmap = await JS.CallAsync<ImageBitmap>("createImageBitmap", blob);

Console.WriteLine($"Bitmap size: {bitmap.Width}x{bitmap.Height}");

// Draw to a canvas context
using var ctx = canvas.GetContext2D();
ctx.DrawImage(bitmap, 0, 0);

// Create from OffscreenCanvas (zero-copy transfer)
using var offscreen = new OffscreenCanvas(256, 256);
using var offCtx = offscreen.Get2DContext();
offCtx.FillStyle = "red";
offCtx.FillRect(0, 0, 256, 256);
using var transferredBitmap = offscreen.TransferToImageBitmap();

// Transfer to a worker (zero-copy, bitmap is Transferable)
worker.PostMessage(bitmap);

// Release resources when done
bitmap.Close();