如何优化 BMP 到 ZPL 的 ASCII 十六进制，就像在标签中使用一样

我想编写一个将位图图像转换为zpl的代码。我为此找到了以下代码：

string bitmapFilePath = @"D:'Demo.bmp";
int w, h;
Bitmap b = new Bitmap(bitmapFilePath);
w = b.Width; h = b.Height;
byte[] bitmapFileData = System.IO.File.ReadAllBytes(bitmapFilePath);
int fileSize = bitmapFileData.Length;
// The following is known about test.bmp.  It is up to the developer
// to determine this information for bitmaps besides the given test.bmp.
int bitmapDataOffset = int.Parse(bitmapFileData[10].ToString()); ;
int width = w; // int.Parse(bitmapFileData[18].ToString()); ;
int height = h; // int.Parse(bitmapFileData[22].ToString()); ;
int bitsPerPixel = int.Parse(bitmapFileData[28].ToString()); // Monochrome image required!
int bitmapDataLength = bitmapFileData.Length - bitmapDataOffset;
double widthInBytes =  Math.Ceiling(width / 8.0);
while(widthInBytes%4 != 0){                               
    widthInBytes++;
}
// Copy over the actual bitmap data from the bitmap file.
// This represents the bitmap data without the header information.
byte[] bitmap = new byte[bitmapDataLength];
Buffer.BlockCopy(bitmapFileData, bitmapDataOffset, bitmap, 0, bitmapDataLength);
string valu2e = ASCIIEncoding.ASCII.GetString(bitmap);
//byte[] ReverseBitmap = new byte[bitmapDataLength];
// Invert bitmap colors
for (int i = 0; i < bitmapDataLength; i++)
{
    bitmap[i] ^= 0xFF;
}
// Create ASCII ZPL string of hexadecimal bitmap data
string ZPLImageDataString = BitConverter.ToString(bitmap);
ZPLImageDataString = ZPLImageDataString.Replace("-", string.Empty);      
// Create ZPL command to print image
string ZPLCommand = string.Empty;
ZPLCommand += "^XA";
ZPLCommand += "^PMY^FO20,20";
ZPLCommand +=
"^GFA, " +
bitmapDataLength.ToString() + "," +
bitmapDataLength.ToString() + "," +
widthInBytes.ToString() + "," +
ZPLImageDataString;
ZPLCommand += "^XZ";
System.IO.StreamWriter sr = new StreamWriter(@"D:'logoImage.zpl", false, System.Text.Encoding.Default); 
sr.Write(ZPLCommand);
sr.Close();

上面的代码运行良好，但问题是它正在生成几乎 4 kb 的 zpl 文件，但相同的文件由大小为 2 kb 的标签转换。我想知道标签在 GFA，a，b，c，数据中使用什么格式。