How to find out the compression of a TIFF image in FreeImage?

I use FreeImage to work with multipage TIFF files and at some point I have a TIFF page, in a FIBITMAP an开发者_如何转开发d I need to know its compression. Any idea how to do this?

FreeImage has no built in function to reveal the tiff file compression scheme, however you can use Exif metadata to figure that out (dib is local FIBITMAP variable, this is c# code):

    public string GetCompressionName()
    {
        long _compression;

        if (dib.IsNull)
           throw new Exception("dib is empty - image haven't been loaded!");

        //Searching tag in metadata.
        ImageMetadata iMetadata = new ImageMetadata(dib);

        foreach (MetadataModel metadataModel in iMetadata)
        {
            if (metadataModel.ToString() == "FIMD_EXIF_MAIN")
            {
                try
                { long.TryParse(metadataModel.GetTag("Compression").ToString(), out _compression); }
                catch
                { return "Unknown"; }


                if (CompressType.ContainsKey(_compression))
                {
                    string _compressionName;
                    CompressType.TryGetValue(_compression, out _compressionName);

                    if (_compressionName != null)
                    {
                        return _compressionName;
                    }
                }
            }
        }

        return "Unknown";
    }

Dictionary<long, string> CompressType = new Dictionary<long, string>()
        { 
            {1, "Uncompressed" } ,
            {2, "CCITT modified Huffman RLE"},
            {32773, "PackBits"}, 
            {3, "CCITT3"},
            {4, "CCITT4"},
            {5, "LZW"},
            {6, "JPEG_old"},
            {7, "JPEG_new"},
            {32946, "DeflatePKZIP"},
            {8, "DeflateAdobe"},
            {9, "JBIG_85"},
            {10, "JBIG_43"},
            {11, "JPEG"},
            {12, "JPEG"},
            {32766, "RLE_NeXT"},
            {32809, "RLE_ThunderScan"},
            {32895, "RasterPadding"},
            {32896, "RLE_LW"},
            {32897, "RLE_HC"},
            {32947, "RLE_BL"},
            {34661, "JBIG"},
            {34713, "Nikon_NEF"},
            {34712,"JPEG2000"}
        };