这似乎可以完成工作.

using System.Drawing;
using System.IO;

namespace wbmp2png
{
    class Program
    {
        static void Main(string[] args)
        {
            foreach (string file in args)
            {
                if (!File.Exists(file))
                {
                    continue;
                }
                byte[] data = File.ReadAllBytes(file);
                int width = 0;
                int height = 0;
                int i = 2;
                for (; data[i] >> 7 == 1; i++)
                {
                    width = (width << 7) | (data[i] & 0x7F);
                }
                width = (width << 7) | (data[i++] & 0x7F);
                for (; data[i] >> 7 == 1; i++)
                {
                    height = (height << 7) | (data[i] & 0x7F);
                }
                height = (height << 7) | (data[i++] & 0x7F);
                int firstPixel = i;
                Bitmap png = new Bitmap(width, height);
                for (int y = 0; y < height; y++)
                {
                    for (int x = 0; x < width; x++)
                    {
                        png.SetPixel(x, y, (((data[firstPixel + (x / 8) + (y * ((width - 1) / 8 + 1))] >> (7 - (x % 8))) & 1) == 1) ? Color.White : Color.Black);
                    }
                }
                png.Save(Path.ChangeExtension(file, "png"));
            }
        }
    }
}