This is really not complicated. So far you've only implemented one half of any statement. Maybe spend more time understanding the statement?
E.g., for the first one: If the color of v(x,y) is black and the colors of q(x,y) and r(x,y) are both white, one of q(x,y) and r(x,y) is selected with equal probability, and the selected pixel is set to black.
if V(x, y) == 0 && q(x, y) == 1 && r(x, y) == 1 %Implements: If the color of v(x,y) is black and the colors of q(x,y) and r(x,y)
if rand >0.5 %implements: one of q(x,y) and r(x,y) is selected with equal probability and set to black
q(x, y) = 0;
else
r(x, y) = 0;
end
end
