Round RBG values to nearest multiple of 50

I have an image I am trying to edit, how would I go about rounding each RBG value to it's nearest multiple of 50 (0, 50,100,150,200, and 250)? I am using a for loop right now that spans the size of the image but I can't figure out if I can use the round function for this or not.

Answer 1

[OCDER]

Try this (no for loop needed):

RGB   = [1 51 76 105 145 160 190 205];
RGB50 = round(a/50)*50;

RGB50 =
   0    50   100   100   150   150   200   200