constructor({ data }) {
    super({ name: 'bKGD', data });
    const dv = new DataView(data);
    if (data.byteLength === 1) {
      defineDataViewProperty(this, 'paletteColor', dv, 8, 0);
    } else if (data.byteLength === 2) {
      defineDataViewProperty(this, 'gray', dv, 16, 0);
    } else {
      defineDataViewProperty(this, 'red', dv, 16, 0);
      defineDataViewProperty(this, 'green', dv, 16, 2);
      defineDataViewProperty(this, 'blue', dv, 16, 4);
    }
  }
A bKGD chunk containing the PNG's background color.