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Re: [Openexr-devel] OpenEXR 2.0 backwards compatibility


From: Ben Woodhall
Subject: Re: [Openexr-devel] OpenEXR 2.0 backwards compatibility
Date: Wed, 15 May 2013 16:54:45 +0100

Our previous version was 1.6.1.

Thanks,  Ben

On 15 May 2013, at 16:51, Ben Woodhall wrote:

Darn.  I must be comparing with 1.6.x.  I shall check which version.

We'll probably want to maintain compatibility with the old software though, so I guess my question remains the same but for maintaining compatibility between 1.6.x and 2.0.

Sorry for the confusion.

Thanks,  Ben


On 15 May 2013, at 16:43, Piotr Stanczyk wrote:

Hi Ben,

I think that behaviour was present in the 1.7.x release. Which version were you building against previously?

Piotr

________________________________________
From: Ben Woodhall address@hidden
Sent: 15 May 2013 08:36
To: address@hidden
Subject: OpenEXR 2.0 backwards compatibility

Hello,

We found an issue when upgrading our EXR libraries to 2.0.  The new libraries automatically use "long names" for the channels if channels are added with names longer than 31 characters.  They set a bit of the version integer in the file header to switch to 255 character channel names.  In earlier EXR libraries these channel names were automatically truncated to 31 characters.  This is perfectly sensible but it means that saving single part images with channel names of more than 31 characters produces EXR 2.0 only images (as previous versions don't support "long names").

We can fix the compatibility by truncating channel names when writing single part files, however we're concerned that there may be other compatibility issue that we should be aware of.  Could you let me know if there are any other compatibility issues?  Is truncating names the right thing to do for backwards compatibility is there a better way to deal with this?

Any help appreciated.

Many thanks,  Ben




-- 
Ben Woodhall
Software Engineer
The Foundry, 6th Floor, The Communications Building,
48 Leicester Square, London, UK, WC2H 7LT
Tel: +44(0)20 7968 6828 - Fax: +44(0)20 7930 8906

The Foundry Visionmongers Ltd.
Registered in England and Wales No: 4642027




-- 
Ben Woodhall
Software Engineer
The Foundry, 6th Floor, The Communications Building,
48 Leicester Square, London, UK, WC2H 7LT
Tel: +44(0)20 7968 6828 - Fax: +44(0)20 7930 8906

The Foundry Visionmongers Ltd.
Registered in England and Wales No: 4642027




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