% imagehist3D
% usage: imagehist3D(pic) or 
% read a jpeg image and split into three RGB components
% and show the 2-compoent histograms
% 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  H = imagehist3D(pic,numbins);

% load picture
[R,G,B,Rmap,Gmap,Bmap] = jpg2rgb(pic,'nopic');
Z = zeros(size(R));

H = hist3D(double(R(:)),double(G(:)),double(B(:)),numbins,numbins,numbins);