Re: EXIF support in PNG [was: Modern compressor]
John Bowler <[email protected]>
| Newsgroups | gmane.comp.graphics.png.general |
|---|---|
| Message-ID | <CAP7U39-ifvCMvSgN7x1wKjcdpiWkbt9jJNA9ZRau+8eCnp-_=w@mail.gmail.com> |
On Sun, Jan 1, 2017 at 6:37 AM, Glenn Randers-Pehrson <[email protected]> wrote: > eXIf * * * The only things I'd add are > > a requirement that only one eXIf chunk be present in a PNG. > It should be made explicit but is there a constraint that there be only one EXIF chunk? This documentation implies that there can only be one: http://dev.exiv2.org/projects/exiv2/wiki/The_Metadata_in_JPEG_files But it states that FlashPix data can be held in multiple APP2 blocks. My guess is that that information is JPEG specific and that there can only be one block. > otherwise there are no ordering constraints beyond those imposed > by the PNG spec > Right; after IHDR, before IEND not in the middle of IDAT. If the chunk isn't recognized there is the added constraint that the order isn't changed with respect to the IDAT stream. I copied the format of ISO-PNG which only gives extra ordering constraints for each chunk. I guess there should probably be a line in the manner of Table 5.3: name multiple ordering ==== ======== ======== eXIf no? None -- John Bowler <[email protected]> +1 (541) 450-9885 PO BOX 3151 KERBY OR 97531-3151 USA ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ png-mng-misc mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/png-mng-misc