apply specific contraction on whole image

sir, I have to take any initial image and apply some contractive function on whole image. for example if I take "rectangle('Position',[0,0,1,1],'FaceColor','r');" and want to apply f(x,y)=(x/2+3*y/8-1/16, x/2+3*y/8+9/16). Plz try to help me.