Alpha.cs

using (StreamWriter writer = new StreamWriter(out))
{
    Image image = Image.FromFile("alpha.png");
    Bitmap bitmap = new Bitmap(image);
    var size = bitmap.Size;
    for (int i = 0; i < size.Width; i++)
    {
        for (int j = 0; j < size.Height; j++)
        {
            var pixel = bitmap.GetPixel(i, j);
            writer.Write(pixel.A == 253 ? "□" : "■");
        }
        writer.WriteLine();
    }
}