% jpg2rgb
% usage: [R,G,B,Rmap,Gmap,Bmap] = jpg2rgb(pic) or 
%        [R,G,B,Rmap,Gmap,Bmap] = jpg2rgb(pic,'nopic')
% read a jpeg image and split into three RGB components
% the three compnents are shown in red, green, and blue
% unless 'nopic' is given
% pic is the name of a jpg file given in 'filename.jpg' format
% typically the component images will be returned as matrices of byte-sized unsigned integers 
% allowing 256 levels for each colour, i.e., 24 bit colour
% Rmap, Gmap and Bmap are colormaps for showing the R,G,B components

function [R,G,B,Rmap,Gmap,Bmap] = jpg2rgb(pic,varagin);

% load picture
X = imread(pic);
R = X(:,:,1);
G = X(:,:,2);
B = X(:,:,3);
M = double(max([max(R(:)),max(G(:)),max(B(:))]));

% define colormaps
Z = zeros(M+1,1);
C = (0:M)'/M;
Rmap = [C,Z,Z];
Gmap = [Z,C,Z];
Bmap = [Z,Z,C];

% show images

if nargin > 1 return, end;

figure(1)
imshow(R,Rmap);
figure(2)
imshow(G,Gmap);
figure(3)
imshow(B,Bmap);
figure(4)
imshow(X);