Subtracting Image from it modified self (by setting zero least significant bit of pixels)

We have a homework of which we need to set the least significant bit of every pixel to zero and then subtract the new image from the original. Here is an example of what I want to do directly from the book.

The code I am trying to use cannot produce image (C) instead it produces a black image.This is my attempt: could anybody point out what im doing wrong please?

 raw = imgetfile;
A = imread (raw);
for k = 0:7
  B = bitset(A, 8-k, 0);
end
C = imsubtract (A,B);

Answer 1

[Image Analyst]

% Set LSB = 0
grayImage2 = grayImage - rem(grayImage, 2);
% Subtract from original
diffImage= double(grayImage) - double(grayImage2);
% Display it.
imshow(diffImage, []);

Note that the image referred to in (c) is simply rem(grayImage, 2) and is just 0's and 1's.

[John Snow]

grayImage/grayImage2 look like figures a/b from the book however diffImage does not look like figure c but instead it looks like this

[Image Analyst]

Setting the LSB to zero will simply round every pixel down to the nearest multiple of 2. For example 131 will go to 130. But if the pixel already had an LSB of 0, it's already an even number and won't change, so if it's 140 it will stay 140. So when you subtract the original you will get 1's where there were odd valued pixels and zero where the pixels were even. Thus the image is just 1's and 0's and is the same as the rem() image. I don't understand how they could get an image that sort of looks grayscale.

[John Snow]

Alright that makes sense.Thank you for your help I will confirm with teacher next week

Answer 2

[Dexian]

How to set MSB=0?What the code in MATLAB?