Why do I receive an error in image write in the imwrite saying I cannot write jpeg file because of signed integer, appreciate it a lot, thanks.

%read image file

A = imread('success.jpg');

%the seed for random noise for some random signal experience

S = RandStream('mt19937ar','Seed',5489);

%signal to noise ratio

snr = -10;

%M-ary Quadrature Amplitude Modulation

M = 8;

k = log2(M);

%data of image to vector

imgvector = A(:);

%vector input into 16-bit binary data where the msb identifies the sign of

%signal

bitt = dec2bin(typecast(int16(imgvector),'uint16'));

%convert binary matrix into an array (column or row array) SERIAL TYPE

[m n] = size(bitt);

array = reshape(bitt,1,m*n);

vector = num2str(array)-'0';

%bits divisible by k by adding zeros

data = length(vector);

r = rem(data,k);

while r~= 0

data = data+1;

r = rem(data,k);

end

conc = horzcat(vector, zeros(1,data-length(vector)));

%binary data to integer valued symbols for qammod where k bit becomes decimal

val = bin2dec(num2str(reshape(conc,k,[])'));

%modulator using QAM

mod = qammod(val,M);

%additive white gaussian noise

noisy = awgn(mod,snr,'measured',S,'db');

%demodulator in QAM

demod = qamdemod(mod,M);

%integer values into binary

demodat = num2str(dec2bin(demod))-'0';

%reshape into serial type

resh = reshape(demodat',1,[]);

%removes the added zero of modulation process

if length(vector) ~= length(resh)

resh(length(vector)+1:data) = [];

end

%original form - array to matrix

org = reshape(resh,m,n);

mat = num2str(org);

%matrix to decimal

dec = typecast(uint16(bin2dec(mat)),'int16');

imwrite(dec,"Rogando_8qam_neg10.jpg");

Answer 1

[Walter Roberson]

https://petapixel.com/2014/01/22/jpeg-standard-gets-boost-will-support-12-bit-color-depth-lossless-compression/

The maximum bits per pixel component for jpeg is 12. 16 bit unsigned images are not supported. Signed integer images are not supported.

Your code typecast whatever the original data was to 16 bit unsigned but makes no attempt to typecast back to the original datatype, which would have been uint8 for jpeg.