Need help creating a grayscale scroll

Hello everyone, I hope you are well. I'm having trouble creating something like this https://www.google.com/search?q=scroll+alpha+grayscale&tbm=isch&ved=2ahUKEwiAovy4u7DmAhUZ04UKHWIoBp4Q2-cCegQIABAC&oqps7 + 34. 12941 … 0.0..0.150.1322.0j10 …… 0 …. 1 ……… 30i10j33i10.AHteCKavXdQ & ei = 82HyXcDcI5mmlwTi0JjwCQ…