I want to convert 183x275x3 matrix of binary bits to decimal bits...bin2dec can not be use..so how should I proceed?

[filename,filepath]=uigetfile({'matlab.jpg'},'C:\Users\anush\OneDrive\Desktop');

selectedImage2 = imread(strcat(filepath, filename));

imshow(selectedImage2);

B2 = dec2bin(selectedImage2);

C2 = reshape(B2',1,numel(B2));

b2= round(selectedImage2./256);

X2 = xor(b2, B2(1:length(b2)));

Y2 = xor(b2, X2);

this is my code for encryption and dcryption of an image

[Walter Roberson]

183x275x3 is not divisible by 8 or 7 or 6. Is it the case that your original image was 183x55x3 and that you are using 5 bits per pixel?

[Anushree Gupta]

Actually, I just started using Matlab....but i guess my original image is also 183x275x3 and i dont have idea about bits per pixel

[Walter Roberson]

B2 = dec2bin(selectedImage2, 8);

Now B2 would be (183*275*3) x 8 and would consist of '0' and '1' (the characters, not the numeric values 0 and 1) .

Your X2 and Y2 would both be class logical: is that your intention? The xor() operation is

xor = @(A,B) (A~=0|B~=0) & ~(A~=0&B~=0)

and neither '0' nor '1' are equal to 0, so both '0' and '1' are considered the same for the purpose of xor. You might perhaps have wanted a bitwise xor. You have some datatype issues to work through as you do the calculation.

[Anushree Gupta]

basically what i want is to convert Y2 in image as its an image bits...but i m getting idea how i proceed

this Xor() operation should i use this elaborately on my code.

i want to convert Y2 from binary to decimal...which is not possible by bin2dec as it works only till 53 digits.

Answer 1

[Walter Roberson]

B2 = dec2bin(selectedImage2, 8) - '0';

to get numeric values. Use bitxor() instead of xor() .

back_to_numeric = reshape(bin2dec(char(reshape(Y2, 8, []) + '0').'), size(selectedImage2));
back_to_numeric = cast(back_to_numeric, class(selectedImage2));

[Anushree Gupta]

I did all this...but its showing error:

Product of known dimensions, 8, not divisible into total number of elements, 150975.

I used bitxor() also in place of xor()

[Walter Roberson]

Your encryption algorithm is faulty.

b2= round(selectedImage2./256); 

gives one bit for each array element in selectedImage2, but B2 has 8 bits for each selected element in selectedImage2, so you have a mismatch in sizes when you go to do the xor. Your code gets around that by taking only a subset of B2 -- note that length(B2) means:

if isempty(B2)
    length is 0
else
    length is max(size(B2))
end

so indexing B2(1:length(B2)) does not extract all of B2. It happens to get the first column of B2 in this case.

Then with you working with only a portion of B2, you do not have enough bits to reconstruct the image.