Some help

hey i am trying to take an image and convert it down to 5 colors and have the resulution be 48x96

i want to select to background to be only orange and only allow the picture to be shown using white, black, a light grey, and a dark grey

i dont know how to do this in photoshop/gimp studios, can anyone help me

it is for a project where im trying to make a logo mosaic

i will not be providing a photo, because it is of a person who has not consented to be posted here