[Libexif-devel] Some questions on the exif tags defined in exif-tag.h

[Jef D. <jef...@ho...>]

I have some questions on the exif tags defined in the file exif-tag.h:

1. Why are the EXIF_TAG_GPS_* tags listed separate from the other tags? 
Shouldn't they be included in the main enum. To my knowledge, it is 
perfectly valid to have duplicate values inside the same enum.

2. There are some tags present which are not listed in the EXIF 2.2 or 
DCF specifications:

EXIF_TAG_NEW_SUBFILE_TYPE
EXIF_TAG_FILL_ORDER
EXIF_TAG_DOCUMENT_NAME
EXIF_TAG_TRANSFER_RANGE
EXIF_TAG_SUB_IFDS
EXIF_TAG_JPEG_PROC
EXIF_TAG_XML_PACKET
EXIF_TAG_CFA_REPEAT_PATTERN_DIM
EXIF_TAG_CFA_PATTERN
EXIF_TAG_BATTERY_LEVEL
EXIF_TAG_IPTC_NAA
EXIF_TAG_IMAGE_RESOURCES
EXIF_TAG_INTER_COLOR_PROFILE
EXIF_TAG_TIFF_EP_STANDARD_ID
EXIF_TAG_GAMMA
EXIF_TAG_UNKNOWN_C4A5

A few of them are listed in the TIFF specification, but not all of them. 
Why are they included? Why are only some TIFF tags included and not all 
of them?