These are all the possible values for the IG_ISIS_TAG_FILETYPE tag.
Values:
| IG_ISIS_FILETYPE_TIFF | TIFF. |
| IG_ISIS_FILETYPE_PDA | PDA. |
| IG_ISIS_FILETYPE_PCX | PCX. |
| IG_ISIS_FILETYPE_PICT | PICT. |
| IG_ISIS_FILETYPE_DCX | DCX. |
| IG_ISIS_FILETYPE_GIF | GIF. |
| IG_ISIS_FILETYPE_BMP | BMP. |
| IG_ISIS_FILETYPE_FILENET | IMG. |
| IG_ISIS_FILETYPE_JPEG | JPEG. |
| IG_ISIS_FILETYPE_JP2 | JPEG 2000. |
| IG_ISIS_FILETYPE_CALS | CALS. |
| IG_ISIS_FILETYPE_DISCORP | CMP. |
| IG_ISIS_FILETYPE_MODCA | MDA, IBM's MO:DCA. |
| IG_ISIS_FILETYPE_TG4 | TG4, Tiled G4. |
| IG_ISIS_FILETYPE_PDF | PDF, portable document format. |
| IG_ISIS_FILETYPE_PLEXUSTIFF | Plexus TIFF format. |
| IG_ISIS_FILETYPE_JBIG | JBG, JBIG data stream. |
| IG_ISIS_FILETYPE_PNG | PNG. |