how do i select data from image smapler?

hi all, i need some help, noobs here

case :

data output that was generated by image sampler (black n white) is 0 - 1

how do i get data 0 - 1 but without 0,3 (for example)

i have try it with some definition like larger than, smaller than, or equals

but they're all just generated true or false

i just want to remove the background data from image sampler

thanks before