BitMiracle / libtiff.net通过压缩将页面复制到其他TIFF

Question

我正在尝试构建一个程序，该程序读取tiff文件，选择多个页面。 提取这些页面并将其放入列表

原始tiff具有TiffCompressOption.Ccitt4压缩。

从不同文件中提取x页后，我想使用tifflib重建tiff。 但是，当我创建tiff时，以相同的压缩率看不到页面（可能是损坏的）。当我用另一种压缩方式（RGB上的LZW和Photometrix）重建它时。它行得通，只有tiff的大十倍。

代码在下面。

        public bool CreateTiff(List<Bitmap> listBitmap, string fileName)
    {

        int numberOfPages = listBitmap.Count;

        using (Tiff output = Tiff.Open(fileName, "w"))
        {

            for (int page = 0; page < numberOfPages; ++page)
            {

                // get bufferData
                var bmp = listBitmap[page];

                byte[] raster = getImageRasterBytes(bmp, PixelFormat.Format32bppArgb);
                output.SetField(TiffTag.IMAGEWIDTH, bmp.Width);
                output.SetField(TiffTag.IMAGELENGTH, bmp.Height);
                output.SetField(TiffTag.COMPRESSION, Compression.CCITT_T6);
                output.SetField(TiffTag.PHOTOMETRIC, Photometric.MINISBLACK);
                output.SetField(TiffTag.ROWSPERSTRIP, bmp.Height);
                output.SetField(TiffTag.XRESOLUTION, bmp.HorizontalResolution);
                output.SetField(TiffTag.YRESOLUTION, bmp.VerticalResolution);
                output.SetField(TiffTag.BITSPERSAMPLE, 8);
                output.SetField(TiffTag.SAMPLESPERPIXEL, 4);
                output.SetField(TiffTag.PLANARCONFIG, PlanarConfig.CONTIG);
                output.SetField(TiffTag.EXTRASAMPLES, 1, new short[] { (short)ExtraSample.UNASSALPHA });

                output.SetField(TiffTag.PAGENUMBER, page, numberOfPages + 1);

                int stride = raster.Length / bmp.Height;

                convertSamples(raster, bmp.Width, bmp.Height);
                for (int i = 0, offset = 0; i < bmp.Height; i++)
                {
                    output.WriteScanline(raster, offset, i, 0);
                    offset += stride;
                }

                output.WriteDirectory();
            }

        }

        Process.Start(fileName);



        return true;
    }

    private static void convertSamples(byte[] data, int width, int height)
    {
        int stride = data.Length / height;
        const int samplesPerPixel = 4;
        for (int y = 0; y < height; y++)
        {
            int offset = stride * y;
            int strideEnd = offset + width * samplesPerPixel;
            for (int i = offset; i < strideEnd; i += samplesPerPixel)
            {
                byte temp = data[i + 2];
                data[i + 2] = data[i];
                data[i] = temp;
            }
        }
    }

    private static byte[] getImageRasterBytes(Bitmap bmp, PixelFormat format)
    {

        Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
        byte[] bits = null;
        try
        {
            // Lock the managed memory
            BitmapData bmpdata = bmp.LockBits(rect, ImageLockMode.ReadWrite, format);
            // Declare an array to hold the bytes of the bitmap.
            bits = new byte[bmpdata.Stride * bmpdata.Height];
            // Copy the values into the array.
            System.Runtime.InteropServices.Marshal.Copy(bmpdata.Scan0, bits, 0, bits.Length);
            // Release managed memory
            bmp.UnlockBits(bmpdata);
        }

        catch
        {
            return null;
        }
        return bits;
    }