Re: [Openexr-devel] Appending to a partially rendered image

[David Aguilar]

On Mon, Jun 17, 2013 at 2:50 PM, Richard Hadsell
<address@hidden> wrote:
> On 06/10/2013 06:01 PM, Richard Hadsell wrote:
>
> When generation of an image is stopped before the image is complete, we
> would like to append more scanlines or tiles to the partial image.  What is
> the most reasonable way to do this?
>
>
> Does a lack of response mean that there is no way to append to an exr file?

Not necessarily, but my answer is not strictly an "append" operation.

Here's one way that might work.  EXR files have a notion of a
"dataWindow" which is separate from the display window; they can be
different.

I'm imagining that you could set the data window to be just the region
that does exist; later you can "append" to the image by reading in the
current data (as defined by the data window) and filling in the
missing regions; eventually the data window will be equal to the
display window size, and the image will be complete.

This implies that you (or one of the apps you use, e.g. Nuke) is not
already using the dataWindow header for something else.  The absolute
safest thing is to invent your own custom header, e.g.
"completedScanlines" or whatever you want to call it, and manage the
custom EXR header yourself.
--
David