Re: EXIF support in PNG
Willem van Schaik <[email protected]>
| Newsgroups | gmane.comp.graphics.png.general |
|---|---|
| Message-ID | <[email protected]> |
On 2017-01-14 10:41, Glenn Randers-Pehrson wrote:
>
> When present, the eXIf chunk contains contains EXIF metadata that is
>
double "contains"
>
> Mode: 1 byte
> 0: the remaining length-1 bytes of data make up a
> zlib-encoded EXIF profile written in accordance
> with chapter 5, "Deflate/Inflate Compression"
> of the PNG specification version 1.2 (which
> is Clause 10.1, "Compression method 0" of the
> ISO PNG specification).
> 69: (ASCII "E") the remaining length-1 bytes of
> data, combined with the byte "E", make up a raw
> uncompressed EXIF profile
>
suggestion ...
69: the Mode byte (ASCII "E") plus the remaining
length-1 bytes in the chunk (that starts with
"xif") make up a raw uncompressed EXIF profile
I like using the "E" that is already at the start of the EXIF data.
Maybe uncompressed should come before compressed.
Why I still don't like the compressed option, is that well behaving PNG
decoding software are required to implement both modes. For example a
simple "png2exif" tool now needs to include a zlib library.
Willem
--
Willem van Schaik
<[email protected]>
http://www.schaik.com/
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