ImageOutput: Behavior when image's format is incompatible with user-specified pixel type

[pouax]

Hi,

When writing images with ImageOutput or ImageBuf, it's possible to specify the target pixel type as a TypeDesc (respectively in the newspec (C++)/spec (Python) parameter for ImageOutput.open , or the dtype parameter for ImageBuf.write).
However, the final selected type ultimately depends on the plugin, as some image formats may be incompatible with the user-specified type.

When this mismatch happens, the plugin silently changes the user selected type and writes the image in its own preferred type, which should best preserve precision.
However, this behavior might be surprising to some users expecting no change of pixel type, or at least no precision loss.

Could there be a way to write the images in a "strict" mode, where OpenImageIO would return an error in these cases instead of changing the target type ?
Or maybe a way to manually check the valid pixel types for the selected plugin before attempting to write the image ?

Thanks !