Excellent suggestion. This could be implemented easily as a custom image property, but given the importance of this feature, maybe I should add it to the XISF specification, as a new optional attribute of the DisplayFunction element. From a practical point of view, this would require slight changes in the platform to make the 24-bit STF option accessible through PCL and PJSR. I'll implement this in the next version of the core application. Thank you!
