Error using BCH encoding scheme

I am trying to encode an image file using BCH encoding scheme using communication toolbox. I am using comn.BCHEncoder function. Problem is the code is showing an error in step function. this is the code -

clc, clear all;
[X,map]= imread('xxxx.jpg');   % read an image 30x30
msg = im2bw(X,map,0.3);
imshow(X,map), figure, %if we don't use figure we can't see the two images
m = 4; n = 2^m-1; % Codeword length = 15
dim=size(msg+0);
%n=double(dim(2)+1);
k=double(dim(2));

msg_d=double(msg);
m=5;
msgN=gf(msg,m);
N=2^n-1;
% decBCH=comm.BCHDecoder;

encBCH = comm.BCHEncoder(n,k);
decBCH=comm.BCHDecoder(n,k);
size_1=dim(1);
BCHEnc=zeros(dim(2)+2,dim(1));
tic
for i=1:size_1
BCHEnc(:,i)=step(encBCH,msg_d(i,:)');
end
toc
MATLAB is showing following error -
step(encBCH,msg_d(1,:)')
Error using BCHEncoder/step
The input and output dimensions must be consistent with the message or codeword length, including the effects of possible puncturing.

if I want to use message matrix [180x30] for example, should I take row by row? What should i use as a value of n and k in comm.BCHEncoder(n,k) then?