como guardar en jpg matlab

close all; % Cerrar todo
clear all; % Limpia todo
clc; % Limpia command window

x=imread ('peppers.jpg');

imwrite(x,'peppers.jpg',... %# JPEG output (lossy): 144,068 byte output file
'Quality',100);

imgjpg = imread('peppers.jpg','JPEG');
imshow(imgjpg);