You can set 3 other parameters by setting specific bits in PIXON_SNR, however it is more straightforward to set those parameters directly. See PIXON_FULL_PM_CALC, PIXON_BACKGROUND_MODEL, and PIXON_VARIABLE_METRIC.
If you want to set all 4 options through this one parameter, PIXON_SNR, then these are the bits you need to set:
Bit 0 - (pixon_snr OR 1, or just set pixon_snr=1) Weight the residuals by the signal-to-noise ratio.
Bit 1 - (pixon_snr OR 2) Do a more complete but slower calculation of the pixon map. Same as PIXON_FULL_PM_CALC.
Bit 2 - (pixon_snr OR 4) Attempt a background estimation from the residuals. Same as PIXON_BACKGROUND_MODEL.
Bit 3 - (pixon_snr OR 8) Use the fast algorithm. Same as PIXON_VARIABLE_METRIC.