setPreviewImage

 public setPreviewImage(imgURL: string): void
  {
    if (this._canvas !== undefined)
    {
      const img: HTMLImageElement = new Image();

      this._url       = imgURL;
      img.crossOrigin = 'anonymous';

      // TODO This only works for a single image load.  As an exercise, modify to handle deletion (including handlers)
      // and re-initializing of a new Image if the setPreviewImage() method is called multiple times
      img.onload = () =>
      {
        // which dimension is binding?
        const w: number = img.width as number;
        const h: number = img.height as number;

        const s1: number = w / this._canvas.width;
        const s2: number = h / this._canvas.height;

        const ctx: CanvasRenderingContext2D = this._canvas.getContext('2d') as CanvasRenderingContext2D;

        let d: number;
        let left: number   = 0;
        let top: number    = 0;
        let right: number  = 0;
        let bottom: number = 0;

        if (s1 >= s2)
        {
          d      = this._canvas.height - (h/s1);
          left   = 0;
          top    = Math.round(0.5*d);
          right  = this._canvas.width;
          bottom = h / s1;
        }
        else
        {
          d      = this._canvas.width - (w/s2);
          left   = Math.round(0.5*d);
          top    = 0;
          right  = w / s2;
          bottom = this._canvas.height;
        }

        ctx.drawImage(img, left, top, right, bottom);

        const data: Uint8ClampedArray = this._canvas.getContext("2d")!.getImageData(left, top, right, bottom).data;

        const n: number = data.length;
        let i: number;

        // process rgb and skip over alpha
        for (i = 0; i < n; i+=4) {
          this._rgbArr.push( {r: data[i], g: data[i+1], b: data[i+2]} );
        }

        this._onLoaded.emit(this._url);
      };

      img.onerror = () => this._onImgError.emit(this._url);

      img.style.display = 'none';
      img.src           = imgURL;
    }
  }

Hi!
You can set the extension of the file to give it code highlights and to make it more readable.
instead of "setPreviewImage" use "setPreviewImage.ts".

Helpful Article! Thank you.