Gray image quantization

I am trying to quantize an image into 12 bit intensity using the below code:

R2D = mat2gray(R2D);             % intensity between [0,1]    Double 
R2D = double(uencode(R2D,12));   % intensity between [0,2^12] integer
PIC = mat2gray(R2D);             % intensity between [0,1]    Double
imshow(pic);

the problem is in 'uencode' function , the input must be in the range of [-1,1], is there a way to do that quantization for input values between [0,1]? may be some changes to the 'uencode' will do job :)

Many thanks

Answer 1

[Alan AF]

Thank you, I found the Solution:

R2D = mat2gray(R2D);
[R2D8,map] = gray2ind(R2D,128); 
pic = ind2gray(R2D8,map);
pic = mat2gray(pic);
imshow(pic);

[Image Analyst]

This does 128 gray levels, not 4096.

Answer 2

[Image Analyst]

How about using code like:

actualMin = double(min(min(imgOriginal)));
actualMax = double(max(max(imgOriginal)));
slope = (desiredMax - desiredMin) / (double(actualMax) - double(actualMin));
scaledImage = slope * (double(imgOriginal) - actualMin) + desiredMin;

[Alan AF]

Thanks for your reply

Actually my intention is to Quantize the Image (i.e store every pixel into an 12 bit integer), is there a way to do that?

many thanks :)

[Image Analyst]

I didn't think that was your intention because at the end you called mat2gray() which forces it into a 0-1 range, which pretty much wipes out quantization - not quite but for most intents and purposes it does. And the quantized intermediate images, you didn't do anything with.