问图像的字节大小在Tiff文件分割和合并后增长

EN

private List<Bitmap> SplitTiff(byte[] imageData)
{
    var bitmapList = new List<Bitmap>();
    var tiffStream = new TiffStreamForBytes(imageData);

    //open tif file
    var tif = Tiff.ClientOpen("", "r", null, tiffStream);

    //get number of pages
    var num = tif.NumberOfDirectories();
    if (num == 1) 
        return new List<Bitmap> 
        { 
            new Bitmap(GetImage(imageData)) 
        };

    for (short i = 0; i < num; i++)
    {
         //set current page
         tif.SetDirectory(i);
         FieldValue[] photoMetric = tif.GetField(TiffTag.PHOTOMETRIC);
         Photometric photo = Photometric.MINISBLACK;
         if (photoMetric != null && photoMetric.Length > 0)
             photo = (Photometric)photoMetric[0].ToInt();

         if (photo != Photometric.MINISBLACK && photo != Photometric.MINISWHITE)
             bitmapList.Add(GetBitmapFromTiff(tif));
         // else
             // bitmapList.Add(GetBitmapFromTiffBlack(tif, photo));// commented temporrarly to fix size issue
     }
     return bitmapList;
}

private static Bitmap GetBitmapFromTiff(Tiff tif)
{
    var value = tif.GetField(TiffTag.IMAGEWIDTH);
    var width = value[0].ToInt();

    value = tif.GetField(TiffTag.IMAGELENGTH);
    var height = value[0].ToInt();

    //Read the image into the memory buffer
    var raster = new int[height * width];
    if (!tif.ReadRGBAImage(width, height, raster))
    {
        return null;
    }

    var bmp = new Bitmap(width, height, PixelFormat.Format32bppRgb);

    var rect = new Rectangle(0, 0, bmp.Width, bmp.Height);

    var bmpdata = bmp.LockBits(rect, ImageLockMode.ReadWrite, PixelFormat.Format32bppRgb);
    var bits = new byte[bmpdata.Stride * bmpdata.Height];

    for (var y = 0; y < bmp.Height; y++)
    {
        int rasterOffset = y * bmp.Width;
        int bitsOffset = (bmp.Height - y - 1) * bmpdata.Stride;

        for (int x = 0; x < bmp.Width; x++)
        {
            int rgba = raster[rasterOffset++];
            bits[bitsOffset++] = (byte)((rgba >> 16) & 0xff);
            bits[bitsOffset++] = (byte)((rgba >> 8) & 0xff);
            bits[bitsOffset++] = (byte)(rgba & 0xff);
            bits[bitsOffset++] = (byte)((rgba >> 24) & 0xff);
         }
    }

    System.Runtime.InteropServices.Marshal.Copy(bits, 0, bmpdata.Scan0, bits.Length);
    bmp.UnlockBits(bmpdata);

    return bmp;
}

public static PrizmImage PrizmImageFromBitmaps(List<Bitmap> imageItems, string ext)
{
     if (imageItems.Count == 1 && !(ext.ToLower().Equals(".tif") || ext.ToLower().Equals(".tiff")))
         return new PrizmImage(new MemoryStream(ImageUtility.BitmapToByteArray(imageItems[0])), ext);

     var codecInfo = GetCodecInfo();
     var memoryStream = new MemoryStream();

     var encoderParams = new EncoderParameters(1);
     encoderParams.Param[0] = new EncoderParameter(Encoder.SaveFlag, (long)EncoderValue.MultiFrame);

     var initialImage = imageItems[0];
     var masterBitmap = imageItems[0];// new Bitmap(initialImage);
     masterBitmap.Save(memoryStream, codecInfo, encoderParams);
     encoderParams.Param[0] = new EncoderParameter(Encoder.SaveFlag,  (long)EncoderValue.FrameDimensionPage);

     for (var i = 1; i < imageItems.Count; i++)
     {
          var img = imageItems[i];
          masterBitmap.SaveAdd(img, encoderParams);
          img.Dispose();
     }

     encoderParams.Param[0] = new EncoderParameter(Encoder.SaveFlag, (long)EncoderValue.Flush);
     masterBitmap.SaveAdd(encoderParams);

     memoryStream.Seek(0, SeekOrigin.Begin);
     encoderParams.Dispose();
     masterBitmap.Dispose();
     return new PrizmImage(memoryStream, ext);
}