Re: libpng warning: eXIf: duplicate - what does it mean?
Ben Bullock <[email protected]> Fri, 11 Dec 2020 15:39:06 +0900
| Newsgroups | gmane.comp.graphics.png.devel |
|---|---|
| Message-ID | <CAN5Y6m8uXpv1Ywa=41DsN34B6Bnqpi_NkixRti7o2W=07Kqe-A@mail.gmail.com> |
On Fri, 11 Dec 2020 at 15:17, Ben Bullock <[email protected]> wrote: > > > On Fri, 11 Dec 2020 at 15:03, Ben Bullock <[email protected]> > wrote: > >> >> What could be causing this error? >> > > Examining the output png file with hexdump, it actually appears to have > two eXIf chunks: > ... > So while the duplicate error seems to be valid, I'm not sure how it got > two chunks. > > What error might I have made which caused this to happen? > In lpng1637, looking at pngwrite.c, png_write_eXIf is called twice, in png_write_end and in png_write_info. https://github.com/glennrp/libpng/blob/libpng16/pngwrite.c#L241 https://github.com/glennrp/libpng/blob/libpng16/pngwrite.c#L443 The other chunks seem to have some kind of protection to stop them from being written twice, but the eXIf chunk structure doesn't seem to have anything like that, nor can I see anything in png_write_eXIf in pngwutil: https://github.com/glennrp/libpng/blob/libpng16/pngwutil.c#L1477 It appears writing the eXIf chunk twice is the normal behaviour? Then why does the error appear when reading the PNG file back again? _______________________________________________ png-mng-implement mailing list png-mng-implement-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org https://lists.sourceforge.net/lists/listinfo/png-mng-implement