decreasing no of gray levels

hi all, can any one tell me how to decrease the no of gray levels in a image.i have to decrease in the powers of 2. regards k.v.swamy.

Answer 1

[Image Analyst]

X is the gray level in Walter's answer. Did you try to do it, like this:???

X = 0:255;
P = 3;
quantizedGrayLevel = X - mod(X,2^P)
fprintf('Original Gray Level,  New Quantized Gray Level\n');
for gl = 1:length(X)
    fprintf('%10d     becomes %10d\n', X(gl), quantizedGrayLevel(gl));
end

Answer 2

[Walter Roberson]

Hint: X - mod(X,2^P)

[k.v.swamy]

can u pl tell me what is x