You’ll need another multiplication.
sl_str_hybr = sl_str * (1 – hybr_contr*I)
sl_str_hybr … new sl_str value
sl_str … scanline strength (from 0 to 1)
hybr_contr … hybrid contrast
I … input intensity (R,G,B or Y) (also from 0 to 1)
You can make the scanline completely disappear at I = 1, i.e. digital 255, if you choose hybr_contr = 1, which is pretty neat. My choices are just for testing and not preset 😉
If you want to simulate, you can download the small program here: https://www.dropbox.com/s/o7u40uij7bgyn7a/sl_test_ossc.m?dl=0
You’ll need MATLAB or Octave to run the script. Octave is freely available.
I’ll share hdl-code once I tested it. I’m not 100% sure that it works with my first implementation attemp as I haven’t written a tenchbench so far.