Re: [Pmt-exif] HEX syntax

[Adam M. C. <am...@cs...>]

Glenn Randers-Pehrson <gl...@ho...> wrote:

> I think we need to say something about the "endian" condition of data
> stored in a HEX string.
>
> ...require that the application writing a HEX string convert it to
> network byte order first.

HEX is used only for the MakerNote subkeyword.  If the encoder does not
understand the layout of the data, then it cannot convert the byte order
of the subfields.  But if it does understand the layout, why stop at
fixing the byte order?  Why not convert it to a human-readable form like
all the other data in the textExif chunk?

> One possibility is to require applications to write a PNG_ByteOrder
> subkeyword (value 0: unknown, 1: BigEndian, 2: LittleEndian)

If it's unknown, why not just omit this subkeyword?  Also, this would be
more human-friendly as:

PNG_HexByteOrder: big-endian
PNG_HexByteOrder: little-endian

or maybe:

PNG_HexEndian: big
PNG_HexEndian: little

Another possibility is to put the information in the HEX value itself:

MakerNote=M 04B129C6
MakerNote=I C629B104

(I took the M/I convention from TIFF.)

AMC