function varargout = histmatch(image,matchhist,mapl)

%    HISTMATCH    直方图规定化函数

%      matchhist为规定直方图，规定图像的灰度级N<=M

%      没有该参数输入，默认为执行直翻图均衡化

%      mapl只有有matchhist参数时才具有意义，为映射规则

%      可以取值为SML和GML，默认为SML

%      无输出默认输出原始图像、原始直方图、规定图像、规定图像直方图

%    $Author: lskyp    $Data: 2009.08.18

error(nargchk(1,3,nargin));

% 没有规定直方图输入，即输入参数只有一个，执行直方图均衡化

if nargin == 1

if nargout == 0

histeq_my(image);

else

[imageeq,grayx,histeq,hist] = histeq_my(image);

varargout = {imageeq,grayx,histeq,hist};

end

else

if nargin == 2

mapl = 'GML';

end

if ~ (strcmp(mapl,'GML') || strcmp(mapl,'SML'))

error('错误的映射规则')

end

if ndims(matchhist) > 2 || (ndims(matchhist) == 2 && (size(matchhist,1) ...

>1 && size(matchhist,2) > 1))

error('错误的规定直方图，规定直方图需为向量')

end

matchhist = matchhist(:);

matchhist = matchhist';

N = length(matchhist);

M = double(intmax(class(image))) + 1;

if N > M

error('错误的规定直方图，规定直方图灰度级需<=原始灰度级')

elseif N < M % 可以视为>N的灰度部分置零

matchhist = [matchhist zeros(1,M - N)];

end

[hist,grayx] = imhist_my(image);

% 归一化

histn = hist/numel(image);

% 原始直方图的累积直方图

histc = cumsum(histn);

% 规定直方图的累积直方图

matchhistc = cumsum(matchhist);

% 映射的实现，Ref. 章毓晋. 图像工程(上册)——图像处理

tk = zeros(1,M); % 映射关系hist-->tk

if strcmp(mapl,'SML')

for k = 1:M

mappingL = zeros(size(matchhist));

for l = 1:N

mappingL(l) = abs(sum(histc(1:k)) - sum(matchhistc(1:l)));

end

[minmap,tk(k)] = min(mappingL);

end

else

for l = 1:N

mappingL = zeros(1,M);

for k = 1:M

mappingL(k) = abs(sum(matchhistc(1:l)) - sum(histc(1:k)));

end

[minmap,tk(l)] = min(mappingL);

end

end

if N < M

for k = N:M

tk(k) = N;

end

end

histm = zeros(1,N);

for k = 1:M

histm(tk(k)) = histm(tk(k)) + hist(k);

end

% 图像的规定化

imagematch = zeros(size(image));

for p = 1:size(image,1)

for q = 1:size(image,2)

ind = image(p,q) + 1;

imagematch(p,q) = tk(ind);

end

end

imagematch = mat2gray(imagematch);

eval(['imagematch = im2' class(image) '(imagematch);'])

graymatch = 0:length(histm) - 1;

% 输出

if nargout == 0

subplot(221)

imshow(image)

title('原始图像')

subplot(222)

imshow(imagematch)

title('直方图规定化后图像')

subplot(223)

stem(grayx,hist,'Marker','none')

xlim([0 max(grayx)]);

xlabel('灰度值')

ylabel('统计个数');

title('原始直方图')

subplot(224)

stem(graymatch,histm,'Marker','none')

xlim([0 max(graymatch)]);

xlabel('灰度值')

ylabel('统计个数');

title('规定化后直方图')

else

varargout = {imagematch,graymatch,histm,grayx,hist};

end

end