Like most animals, pigs are more sensitive to movement rather than actually seeing & determining a human threat. I do however think they have reasonable eye sight.
On my place there's a ridgeline vehicle track where I drive my buggy to access different parts of my farm. If I'm skylighted on the ridgeline track I've had pigs 800 yards away start to run.
I have also sat on a rocky outcrop in cleared paddock with the wind in my face & wearing no cammo & had a mob of 9 mid size pigs feed straight past me, all within 3 to 15 yards.