Some tiffs (Big Endian with fax compression) are showing up as x-tarr

I have found that a certain tiff that we manage is now reporting application/x-tar in Tika where it previously reported as a tiff (image/tiff). 

Observe this code in ArchiveStreamFactory, detect method.

  // COMPRESS-117 - improve auto-recognition

        if (signatureLength >= TAR_HEADER_SIZE) {

            TarArchiveInputStream tais = null;

            try {

                tais = new TarArchiveInputStream(new ByteArrayInputStream(tarHeader));

                // COMPRESS-191 - verify the header checksum

                if (tais.getNextTarEntry().isCheckSumOK())

{                     return TAR;                 }

            } catch (final Exception e)

{ // NOPMD // NOSONAR                 // can generate IllegalArgumentException as well                 // as IOException                 // autodetection, simply not a TAR                 // ignored             }

finally

{                 IOUtils.closeQuietly(tais);             }

What if find is that most TIFs, when they get to tais.getNextTarEntry() fail with an exception (i.e fall into the "simply not a tar" case). However this tiff actually does NOT fail here. This somewhat makes sense as the internal structure of a fax compressed tifs as a tar-like structure

Note, the CompositeDetector class eventually does recognize it as a proper tiff as it loops through its detectors in its detect method. It is detected as tiff in the MimeTypes class, which is one of the implementations of the Detector interface

 

    public MediaType detect(InputStream input, Metadata metadata)

            throws IOException {

        MediaType type = MediaType.OCTET_STREAM;

        for (Detector detector : getDetectors()) {

            //short circuit via OverrideDetector

            //can't rely on ordering because subsequent detector may

            //change Override's to a specialization of Override's

            if (detector instanceof OverrideDetector &&        metadata.get(TikaCoreProperties.CONTENT_TYPE_OVERRIDE) != null)

{                 return detector.detect(input, metadata);             }

            MediaType detected = detector.detect(input, metadata);

            if (registry.isSpecializationOf(detected, type))

{                 type = detected;             }

        }

        return type;

However since Image/tiff isn't a specialization of application/x-tar it does not replace the type with tiff.

My fix was to add a  "<sub-class-of type="application/x-tar"/>" to the definition for image/tiff in the tika-mimetypes.xml file