I just found Yushatak's scaler thread ( Where are the scalers (in the code)? ) but I'm still trying to wrap my ahead around DOSBox's scaler architecture.

Is there a way to differentiate between even and odd pixels? I'm trying to hack something together that averages each pair of horizontally-adjacent pixels. Here's an oversimplified example:

10 8 4 6 8 2 0 6 10 0

would be changed to

9 9 5 5 5 5 3 3 5 5