I switched to the save() method because otherwise the ColorSpace settings influenced the saved temp images.jensverwiebe wrote: ↑Thu Feb 08, 2018 7:34 pm Remember our discussion when i wanted hdri cached as exr ? ( was also png )
In the commit you linked I now see that we circumvented this problem by changing the Colorspace settings temporarily.
Whatever, I think saving the original format with save() is better. It should solve your problem because every image is now saved with it's original format. We sort of load off the problem to Blender.
So I guess Blender also uses OIIO, tries to save DDS and fails because it's not implemented, so the files are 0 bytes.
We can check for DDS files and use the old method to save a PNG in that case, however it's not high priority for me because I think the number of users using DDS in Blender is very small.