For the comment to be saved:
L_DeleteComment
L_GetComment
L_SetComment
L_WriteFileComment
For the comment in an existing file:
L_ReadFileComment
L_ReadFileCommentMemory
L_ReadFileCommentOffset
L_WriteFileCommentExt
For the TIFF tag to be saved:
L_GetTag
L_SetTag
L_WriteFileTag
For the TIFF tag in an existing file:
L_EnumFileTags
L_ReadFileTag
L_CommentsSupported
L_FreeFileComments
L_FreeFileTags
L_GeoKeysSupported
L_ReadFileComments
L_ReadFileGeoKeys
L_ReadFileTags
L_TagsSupported
L_ReadFileTagMemory
For the FlashPix Comments:
L_GetFileCommentSize
L_ReadFileCommentExt