J. P. Gilliver (John) wrote:
In message , R.Wieser
writes:
John,

_Does_ the .png format _have_ a metadata text field?

Yes. The below document describes the iTXt, tEXt, and zTXt "chukns",
which
can be used to store such data.

https://dev.exiv2.org/projects/exiv2...a_in_PNG_files

Thanks. You, Java Jive, and Paul have confirmed that.

If so, what utility lets you see it, and ideally edit it?

I'm sorry, but I have absolutily no idea. Depending on your version of
Windows you might be able to add/edit them using :

rightclick on the image - properties - summary

(Doesn't work under XP)

Nor 7 (there is no "summary" tab [or even a "Summary" one]).

Java Jive said he used Paint Shop Pro to add some "information" to a
.png, and since he said he found the "strings" in the file afterwards, I
presume he meant text. I think I have PSP somewhere (IIRR even a Big
Version they made available when they wanted to close down servers or
something, though that may be something else), but it seems a bit of a
sledgehammer to load it just for this.

If not, try a google for "png edit exif" (EXIF is a kinda metadata
standard).

Regards,
Rudy Wieser


I'm just doing that. www.thexifer.net seems to be a web-based one.
ExifTool is a command line one, though there are GUI ones that use it.
Exif Pilot (https://www.colorpilot.com/exif.html) looks promising and
small (and free), and claims to do .png ... Trying: yes, seems to work.
(There's a "Comment" field. From the layout - it's a single line - there
might well be a size limit, and I suspect it won't allow line feeds.)

Had a term in the licence I haven't seen befo something like "you may
not use previous versions". I poked around in it and couldn't see any
mention of updates, but that doesn't mean it doesn't automatically get
them. (For the rare times I'm likely to use it, I CBA to be bothered.)

This is a sample image with old-style metadata in a PNG.

https://i.stack.imgur.com/UiagX.png

identify -verbose UiagX.png

Properties:
Author: Hans Müller
Date: 2010-12-08 09:45
date:create: 2010-12-08T13:15:43+01:00
date:modify: 2010-12-08T13:15:43+01:00
Desc: A long time ago in a galaxy far far away....
signatu 3b4a54202316a7ae4b4fe0e431d47958181f4bb89349335582 0d4ba74f9f5ee3

It's possible the Desc is the "Comment" capability.

I could also find a reference to "tools doing naughty things",
such as taking EXIF data and stuffing it into old-style metadata
carriage.

This just makes it harder for other tools to do a good
job on incoming files.

There are supposed to be sample files with the EXIF proposal
for PNG, but I couldn't find them.

Adding a comment to the file might be easier than adding
a clutch of standard EXIF values. In theory, adding EXIF
values would be better for federated search indexing,
but you know how sketchy Windows support is for that
stuff anyway (only "standard" EXIF fields are indexed).

*******

https://en.wikipedia.org/wiki/ExifTool

https://exiftool.org/

ExifTool is also available as a stand-alone Windows executable:

(Note that these versions contain the executable only, and do
not include the HTML documentation or other files of the
full distribution above.)

Windows Executable: exiftool-11.86.zip (6.2 MB)

The stand-alone Windows executable does not require Perl.

Just download and un-zip the archive then double-click on
"exiftool(-k).exe" to read the application documentation,
drag-and-drop files and folders to view meta information,
or rename to "exiftool.exe" for command-line use. Runs on
all versions of Windows.

(Note: Oliver Betz provides an alternate ExifTool Windows
installer that avoids some problems of the self-extracting
archive version above)

That sounds like fun :-/

Paul