Details of three TIFF Tag extensions that Microsoft Office Document Imaging (MODI) software may write into the TIFF files it generates

Microsoft Office Document Imaging (MODI) software includes specific tags/constants in the documents it generates, of which some are enumerated here.  In addition to these enumerated tags there are some undocumented TIFF tag extensions that MODI may write into TIFF documents.

The following information details three of these TIFF tags (37679, 37681, 37680), and you can find corresponding sample source files here, which are provided to aid in implementation.

Tag 37679 contains plain text reflecting the contents of the page image in the TIFF file. This text can either come from an OCR operation on the image or directly from the document content if the TIFF file was produced by the “Microsoft Office Document Image Writer” virtual printer.

Tag 37681 contains positioning information which describes where the text from Tag 37679 appears on the page, as well as information about the position of other objects such as images, tables, and hyphens. The information in this tag is used by the MODI application to enable its text selection feature.

Tag 37680 contains a binary dump of an OLE Property Set Storage. The complete specification of property set storages can be found here. An OLE Property Set Storage is a particular kind of Compound File. The complete specification of the Compound File Binary File Format can be found here.

The easiest way to understand the properties that can be stored in this tag and how to read them is to examine the provided sample source code.

The sample code makes use of the following Windows APIs to extract the data from the file into memory and map a Property Set Storage interface onto it. Developers who want to read this OLE property set storage on platforms other than Windows can use the above mentioned specifications to write their own APIs that perform equivalent functions. More documentation for each of these APIs may be found on MSDN.

· GlobalAlloc to allocate memory (the C runtime function malloc does not return an HGLOBAL and thus isn’t sufficient for this particular purpose. The sample code uses malloc when it can).

· GlobalLock to get a pointer from the handle returned by GlobalAlloc.

· GlobalUnlock after reading data from the file into the pointer returned by GlobalLock.

· CreateILockBytesOnHGlobal followed by StgOpenStorageOnILockBytes to wrap the data in an IStorage.

· StgCreatePropSetStg to get an IPropertySetStorage interface.

A Property Set Storage contains multiple Property Storages. These Property Storages are identified by GUIDs whose names in the code are prefixed with the string FMTID.

The sample code shows how to call the IPropertySetStorage::Open method to extract an IPropertyStorage for each FMTID. The sample code reads each property from the IPropertyStorage using the IPropertyStorage::ReadMultiple method.

The actual numeric values of the GUIDs are in the provided sample code. The four FMTIDs included in this Property Set Storage are:

· FMTID_EPAPER_PROPSET_DOC

· FMTID_NBDOC_PROPSET_DOC

· FMTID_EPAPER_PROPSET_IMAGEGLOBAL

· FMTID_SummaryInformation

FMTID_SummaryInformation is a standard Windows FMTID, and you can find its definition here.

The following information concerns the other three FMTIDs.

These are the properties in FMTID_EPAPER_PROPSET_DOC

Property ID	Type	Meaning
0x0002	VT_UI4	This value exists for backward compatibility with earlier products. Current implementations of MODI always write 0x0000, and so should any third-party producer of these files.
0x0006	VT_UI2	The Unicode character to be used when representing text that has been rejected by the OCR system, for example when coping from the MODI viewer and pasting into a plain text editor such as Notepad.
0x000F	VT_UI4	The number of errors found during the OCR process.
0x0010	VT_UI4	The quality of the OCR result, from 0 to 1000. Higher numbers indicate higher confidence.
0x0014	VT_UI4	The LCID under which OCR was performed. You can find a list of LCID constants here.
0x0015	VT_UI4	Number of paragraphs of text
0x0016	VT_UI4	Number of lines of text
0x0017	VT_UI4	Word count (including recognized and unrecognized words)
0x0018	VT_UI4	Character count (including recognized and unrecognized characters)
0x001B	VT_UI4	The major revision of the software that generated this file. MODI always writes 0x0002.
0x001C	VT_UI4	The minor revision of the software that generated this file. MODI always writes 0x0000.
0x001E	VT_STORAGE	This storage contains the contents of the File-Properties dialog from the Microsoft Office Document Imaging application. See the sample code functions PstgPropSetFromProp and DbgDumpStandardProps for an example of how to extract this property set and read it.
0x01F	VT_UI4	Status of OCR in this file. Must have one of the following values: 0: OCR was not done 1: OCR was completed 2: OCR was attempted 3: OCR found no text

The following are the properties of FMTID_NBDOC_PROPSET_DOC

Property ID	Type	Meaning
2	VT_BLOB	This structure is defined in the sample code, see the function HrReadStationaryData and the structure called NB_STATIONERY_DATA.
3	VT_R4	Page width, in inches
4	VT_R4	Page height, in inches
5	VT_UI2	Language of the document, found here.
6	VT_UI4	The major revision of the software that generated this file. MODI always writes 0x0002.
7	VT_UI4	The minor revision of the software that generated this file. MODI always writes 0x0000.

The following are the properties of FMTID_EPAPER_PROPSET_IMAGEGLOBAL

Property ID	Type	Meaning
2	VT_ISTREAM	This stream contains a dictionary that maps images used during OCR to the text it was recognized as.
3	VT_ISTREAM	This stream contains embedded fonts.

Comments

• Anonymous
  August 16, 2011
  Can you please provide a link to the sample code you have alluded to here. The link seems to be broken. How can we read Tag 37680 from a TIFF file and then process that further? regards