PNG-EXIF support in exiftool

On 10 February 2017 at 09:09, Phil Harvey <phil-CIeU6mJ2MbMd166Dz3SrqbDks+cytr/[email protected]> wrote:
> Just FYI in case anyone wants to play with eXIF/zXIF, the latest version of ExifTool supports reading and writing both eXIF and zXIF (add the -z option when writing to create the compressed zXIF):
>
> http://owl.phy.queensu.ca/~phil/exiftool/

Thanks. I just gave a try to version 10.42, and it does produce the
new chunks indeed.

Here are a few observations:

The compressed ("zXIF") form produced by exiftool does not have a
valid zlib stream. Maybe it is a deflate stream without the zlib
stream header? It should have the zlib header, like IDAT, iCCP and
zTXt do.

For the uncompressed EXIF chunk at least, the latest draft proposal is here:
http://www.simplesystems.org/png-group/proposals/eXIf/png-proposed-eXIf-chunk-2017-0210a.html

One last thing: could you please avoid using any public chunk names
(like "eXIF" and "zXIF", with second letter in uppercase) until a
public chunk gets voted in? As mentioned in the draft documents, the
unregistered name can be used in test implementations, and that name
is "exIf" for uncompressed, and "zxIf" (or more recently "zxIF") for
compressed. The second letter should be lowercase.

Sincerely,
Cosmin

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