Add fallback option class (currently unused)

src/ext/lib/aard/gl/FallbackCanvas.ts

@@ -0,0 +1,32 @@
+import { GlCanvas, GlCanvasOptions } from './GlCanvas';
+
+
+export class FallbackCanvas extends GlCanvas {
+
+  context: CanvasRenderingContext2D;
+
+  constructor(options: GlCanvasOptions) {
+    super(options);
+    this.context = this.canvas.getContext('2d');
+  }
+
+  /**
+   * We need to override the following methods in order to avoid default behaviour,
+   * since these methods in GlCanvas touch some webGL properties that we cannot really
+   * touch in this class.
+   */
+
+  destroy() {  }
+
+  protected initWebgl() {  }
+
+  drawVideoFrame(video: HTMLVideoElement) {
+    this.context.drawImage(video, this.context.canvas.width, this.context.canvas.height);
+  }
+
+  getImageData() {
+    this.frameBuffer = this.context.getImageData(0,0,this.context.canvas.width,this.context.canvas.height).data as any as Uint8Array;
+    return this.frameBuffer;
+  }
+
+}

src/ext/lib/aard/gl/GlCanvas.ts

@@ -71,7 +71,7 @@ export class GlCanvas {
 
   private frameBufferSize: number;
   private _frameBuffer: Uint8Array;
-  private set frameBuffer(x: Uint8Array) {
+  protected set frameBuffer(x: Uint8Array) {
     this._frameBuffer = x;
   }
   public get frameBuffer(): Uint8Array {
@@ -118,7 +118,7 @@ export class GlCanvas {
   }
 
   /**
-   * Reads pixels from the canvas
+   * Reads pixels from the canvas into framebuffer, and returns pointer to the framebuffer
    * @returns
    */
   getImageData(): Uint8Array {
@@ -156,7 +156,7 @@ export class GlCanvas {
     this.gl.deleteTexture(this.texture);
   }
 
-  private initWebgl() {
+  protected initWebgl() {
     // Initialize the GL context
     this.gl.clearColor(0.0, 0.0, 0.0, 1.0);
     this.gl.clear(this.gl.COLOR_BUFFER_BIT);