What is first bytes for first three commands

[Rombersoft]

I don't know TypeScript but I very need to develop print Image on StarTUP 900 printer.
I use .net/C# lang.
There is function from this project:

raster(image: Image, mode: RasterMode = 'NORMAL') {
    if (!(image instanceof Image))
      throw new TypeError('Only escpos.Image supported');
    mode = utils.upperCase(mode);
    if (mode === 'DHDW' ||
      mode === 'DWH' ||
      mode === 'DHW') mode = 'DWDH';
    const raster = image.toRaster();
    const header = _.GSV0_FORMAT[`GSV0_${mode}` as const];
    this.buffer.write(header);
    this.buffer.writeUInt16LE(raster.width);
    this.buffer.writeUInt16LE(raster.height);
    this.buffer.write(raster.data);
    return this;
  };

So, can anybody send me bytes for these three commands:

this.buffer.write(header);
this.buffer.writeUInt16LE(raster.width);
this.buffer.writeUInt16LE(raster.height);

???
In the case when Image has size 384x384 pixels