imhist.m

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function [yout,x] = imhist(varargin)
%IMHIST Display histogram of image data.
%   IMHIST(I,N) displays a histogram with N bins for the
%   intensity image I above a grayscale colorbar of length N. If
%   you omit the argument, IMHIST uses a default value of N=256
%   if I is a grayscale image, or N=2 if I is a binary image.
%
%   IMHIST(X,MAP) displays a histogram for the indexed image
%   X. This histogram shows the distribution of pixel values
%   above a colorbar of the colormap MAP. The colormap must be at
%   least as long as the largest index in X. The histogram has
%   one bin for each entry in the colormap.
%
%   [COUNTS,X] = imhist(...) returns the histogram counts in
%   COUNTS and the bin locations in X so that stem(X,COUNTS)
%   shows the histogram. For indexed images, it returns the
%   histogram counts for each colormap entry; the length of
%   COUNTS is the same as the length of the colormap.
%
%   Class Support
%   -------------
%   The input image can be of class uint8 or double.
%
%   Example
%   -------
%        I = imread('pout.tif');
%        imhist(I)
%
%   See also HISTEQ, HIST.

%   Clay M. Thompson 7-7-92, partially mex-ified by
%   Joseph M. Winograd, 7-93
%   Updated for MATLAB 5, IPT 2 by Steven L. Eddins, 1996
%   Copyright 1993-1998 The MathWorks, Inc.  All Rights Reserved.
%   $Revision: 5.10 $  $Date: 1997/11/24 15:35:25 $

[a, n, isScaled, top, map, err_msg] = parse_inputs(varargin{:});
if (~isempty(err_msg))
    error(err_msg);
end

y = imhistc(a, n, isScaled, top); % Call MEX file to do work.
x = (1:n)';

if (nargout == 0)
    isUint8 = isa(a, 'uint8');
    plot_result(x, y, map, isScaled, isUint8);
else
    yout = y;
end


%%%
%%% Function plot_result
%%%
function plot_result(x, y, cm, isScaled, isUint8)

n = length(x);
stem(x,y)
hs = gca;
h = get(hs,'children');
delete(findobj(h,'flat','Marker','o')) % Remove 'o's from stem plot
limits = axis;
limits(1) = 0.5;
limits(2) = n+0.5;
var = sqrt(y'*y/length(y));
limits(4) = 2.5*var;
axis(limits);

% Get axis position and make room for color strip.
pos = get(hs,'pos');
stripe = 0.075;
set(hs,'pos',[pos(1) pos(2)+stripe*pos(4) pos(3) (1-stripe)*pos(4)])
set(hs,'xticklabelmode','manual')
set(hs,'xticklabel','')

% Create axis for stripe
ax = axes('Position', [pos(1) pos(2) pos(3) stripe*pos(4)]);
limits = axis;

% Create color stripe
if isScaled,
    binInterval = 1/n;
    xdata = [binInterval/2 1-(binInterval/2)];
    if isUint8,
        xdata = 255*xdata;
        limits(1) = 0;
        limits(2) = 255;
    else
        limits(1) = 0;
        limits(2) = 1;
    end
    image(xdata,[0 1],repmat((1:n)/n,[1 1 3]));
else
    image([1 n],[0 1],1:n); colormap(cm)
    limits(1) = 0.5;
    limits(2) = n + 0.5;
end
set(gca,'yticklabelmode','manual')
set(gca,'yticklabel','')
axis(limits);
j=line(limits([1 2 2 1 1]),limits([3 3 4 4 3]));set(j,'linestyle','-')
set(j,'color',get(gca,'xcolor'))

% Set active axis to histogram
axes(hs)
set(gcf,'Nextplot','replace')


%%%
%%% Function parse_inputs
%%%
function [a, n, isScaled, top, map, err_msg] = parse_inputs(varargin)

defaultN = 256;
err_msg = '';

switch nargin
case 0
    a = [];
    n = [];
    isScaled = [];
    top = [];
    map = [];
    err_msg = 'Too few inputs to IMHIST';
    
case 1
    a = varargin{1};
    if (isa(a,'double'))
        n = defaultN;
        isScaled = 1;
        top = 1;
        map = [];
        
    elseif (isa(a,'uint8'))
        if (islogical(a))
            n = 2;
            isScaled = 1;
            top = 1;
            map = [];
            
        else
            n = 256;
            isScaled = 1;
            top = 255;
            map = [];
        end
    end
    
case 2
    a = varargin{1};
    if (prod(size(varargin{2})) == 1)
        % IMHIST(I, N)
        if (isa(a,'uint8'))
            if (islogical(a))
                a = varargin{1};
                n = varargin{2};
                isScaled = 1;
                top = 1;
                map = [];
            else
                a = varargin{1};
                n = varargin{2};
                isScaled = 1;
                top = 255;
                map = [];
            end
        else
            a = varargin{1};
            n = varargin{2};
            isScaled = 1;
            top = 1;
            map = [];
        end
        
    elseif (size(varargin{2},2) == 3)
        a = varargin{1};
        n = size(varargin{2},1);
        isScaled = 0;
        top = n;
        map = varargin{2};
        
    else
        
        a = [];
        n = [];
        isScaled = [];
        top = [];
        map = [];
        err_msg = 'Invalid second input argument';
        
    end
    
otherwise
    a = [];
    n = [];
    isScaled = [];
    top = [];
    map = [];
    err_msg = 'Too many input arguments';
    
end