@miric2 How did you find the -CustomRenderer tag? When I set it, Photos still doesn't show the HDR badge.

Thank you! Yes, this is filed under FB10151072.

Correct. But it also creates a Metal context by default if you just use CIContext(). You would need to have a Metal-based context anyways if you want to use Metal Core Image kernels.

To sample in the middle of the pixel. For instance, if your sampler would use linear sampling, the coordinate 1.0 would return a mix of the first and the second pixel since it's between those pixels. 1.5 would only return the color value of the second pixel.

Can you please try creating a larger image (16x16, for instance) and try again? I was also observing strange behavior (see above) for small EXR images. It would be interesting if these issues are related.