The type of compression used in a TIFF is stored in TIFF Tag 259. You can use the Atalasoft.Imaging.Metadata.TiffTagCollection.GetSingleTag method to retrieve this value. Here is a code example:

[C#]

ushort comp = (ushort)TiffDecoder.GetTiffTag(259, filename, FrameIndexHere).Data;
switch(comp)
{
     case 1:     // None
          break;
     case 2:     // CCITT modified Huffman RLE
          break;
     case 3:     // CCITT Group 3 fax encoding
          break;
     case 4:     // CCITT Group 4 fax encoding
          break;
     case 5:     // Lempel-Ziv & Welch (LZW)
          break;
     case 6:     // 6.0 Old Style JPEG
          break;
     case 7:     // JPEG DCT compression
          break;
     case 32773: // Macintosh RLE
          break;
     case 32946: // Deflate
          break;
}

[Visual Basic]

Dim comp As Integer = Convert.ToInt32(TiffDecoder.GetTiffTag(259, FileName, FrameIndexHere).Data)
Select Case comp
     Case 1          ' None
     Case 2          ' CCITT modified Huffman RLE
     Case 3          ' CCITT Group 3 fax encoding
     Case 4          ' CCITT Group 4 fax encoding
     Case 5          ' Lempel-Ziv & Welch (LZW)
     Case 6          ' 6.0 Old Style JPEG
     Case 7          ' JPEG DCT compression
     Case 32773  ' Macintosh RLE
     Case 32946  ' Deflate
End Select

NOTE: TIFF is a multipage file format.. it is possible for each page in a single TIFF file to have its own compression. This means a single TIFF may not have all compression the same.. there's not really such a thing as a "CCITT Group 4 Compressed Tiff file" so much as it would be "A TIFF File with all pages compressed using CCITT Group 4 Fax Compression". The difference is subtle but important from a technical perspective.

Original Article:

Q10061 - INFO: Is there a way I can tell which compression was used in a TIFF file?