TIFFTagLocation

TIFFTagLocation is a designation used in TIFF and Exif metadata handling to describe where a tag’s data is stored within a TIFF file or its related metadata directories. It is used by software libraries such as libtiff to interpret and read or write tag values correctly.

In the TIFF format, each tag entry within an Image File Directory (IFD) contains a tag ID, data type, count, and a value or an offset. If the data for a tag fits in the 4-byte value field, it is stored directly there; otherwise, the tag’s value is stored at an offset to a separate data area. TIFFTagLocation enumerates the possible storage contexts for a tag, typically corresponding to different IFDs or sub-IFDs.

Common location categories include the main image IFD (the primary IFD that contains general image tags) and specialized sub-IFDs such as the Exif IFD, GPS IFD, and Interoperability IFD. Some implementations also include maker notes or thumbnail IFDs as distinct locations. The exact set of locations can vary between libraries, but the concept remains the same: the location indicates where the tag’s actual data resides so that reading software can locate and interpret it correctly.

Usage and purpose summarize to: TIFFTagLocation helps tag processing routines determine how to fetch, interpret, and, when writing, place the tag data and its offset within the TIFF/Exif metadata structure. See also TIFF, Exif, IFD, and LibTIFF.