RE: [Openexr-devel] Long Channel Names

[Nick Porcino]

One possible solution is to embed an ascii representation of a CRC32 in the 32 
characters. You could store a dictionary somewhere that would allow you to look 
up the original very long names. That would help to keep the EXR files as small 
as possible, a concern to us in the games industry, with our limited RAM 
resources.

-----Original Message-----
From: Charles Henrich [mailto:address@hidden
Sent: Friday, August 15, 2003 9:29 AM
To: Paul Schneider
Cc: address@hidden
Subject: Re: [Openexr-devel] Long Channel Names


On the subject of Re: [Openexr-devel] Long Channel Names, Paul Schneider
stated:

Can we get this changed before this gets so widely adopted that its causing
troubles for the next 100 years? :)  We routinely generate images with large
channel names, and I could easily imagine going over 32 characters.  If it has
to be a fixed field width, 1024 would be a safer upper bound (or even 256, but
please please not 32).  Thanks guys!

> You're talking about channel names, not file names, right?  That's got
> nothing to do with FSSpecs.  The EXR format was actually designed on the SGI
> and ported to the Mac later, so there aren't any Mac anachronisms in the
> format (hopefully not too many unix-isms either).  32 is just a commonly
> used number for "string that probably isn't more than one word".
> 
> Lee, if you change the length of the fixed-size name in your build of
> exrlib, I would expect that other software would crash when trying to read
> your non-standard files.  The EXR format allows you to add arbitrary
> attributes to the file's header, including string attributes of arbitrary
> length.  Could your driver encode the information you need in string
> attributes, rather than channel names?  Perhaps you could use some kind of
> scheme where your channel names are "1", "2", etc, and there is a string
> attribute for each channel with the real name.  See ImfStringAttribute.h for
> more information.
> 
> - Paul
> 
> On Friday, August 15, 2003, at 07:13 AM, Darrin Cardani wrote:
> 
> >At 2:54 PM +0100 8/15/03, Lee Kerley wrote:
> >>I'm new to OpenEXR development, but I have a display driver for prman that
> >>writes out EXR files.  The problem is that when I output secondary outputs
> >>from my prman render the name of the channel get's quite long.  I've
> >>noticed in the code that there is a limit of 32 characters.  Is there any
> >>reason why this maximum name length is so short. I accept that in most
> >>circumstances that a channel name would normally be quite short, but in
> >>thius situation I need it to be longer.  I have altered the size of SIZE
> >>define in ImfName.h to 1024, in my own build, but would like to request
> >>that this change be included in further releases of OpenEXR.
> >>
> >>On a more immediate note, are there any implications with me changing this
> >>variable to 1024 as opposed to it's default setting of 32?
> >
> >I'm guessing this is an artifact of the Mac OS FSSpec structure which is
> >used to specify a file. Newer versions of the OS (OS 9 and above, I
> >believe) can support longer file names, but there's still a lot of code out
> >there using the old structures. So the obvious consequence is that if you
> >change it, there's a chance that you won't be able to use those files on a
> >Mac.
> >
> >Darrin -- Darrin Cardani - address@hidden President, Buena Software,
> >Inc.  <http://www.buena.com/> Video, Image and Audio Processing Development
> >
> >
> >_______________________________________________ Openexr-devel mailing list
> >address@hidden
> >http://mail.nongnu.org/mailman/listinfo/openexr-devel
> 
> 
> 
> _______________________________________________ Openexr-devel mailing list
> address@hidden
> http://mail.nongnu.org/mailman/listinfo/openexr-devel

       Charles Henrich           Digital Domain          address@hidden

                         http://www.sigbus.com/~henrich


_______________________________________________
Openexr-devel mailing list
address@hidden
http://mail.nongnu.org/mailman/listinfo/openexr-devel