数字图像处理MATLAB实现（第2版）冈萨雷斯书中代码-2.1intrans函数持续更新。。。
function g = intrans(f, method,varargin)
%INTRANS Performs intensity (gray-level) transformations.
%  G = INTRANS(F, 'neg') computes the negative of input image F.
%
%  G = INTRANS(F, 'log', C, CLASS) computes C*log(1 + F) and
%  multiplies the result by (positive) constant C. If the last two
%  parameters are omitted, C defaults to1. Because the log is used
%  frequently to display Fourier spectra, parameter CLASS offers the
%  option to specify the class of the output as 'uint8' or
%  'uint16'. If parameter CLASS is omitted, the output is of the
%  same class as the input.
%
%  G = INTRANS(F, 'gamma', GAM) performs a gamma transformation on
%  the input image using parameter GAM (a required input).
%
%  G = INTRANS(F, 'stretch', M, E) computes a contrast-stretching
%  transformation using the expression 1./(1 + (M./(F +
%  eps)).^E).  Parameter M must be in the range [0, 1].  The default
%  value for M is mean2(im2double(F)), and the default value for E
%  is4.
%  G = INTRANS(F, 'specified', TXFUN) performs the intensity
%  transformation s = TXFUN(r) where r are input intensities, s are
%  output intensities, and TXFUN is an insensity transformation (mapping)
%  function, expressed as a vector with values in the range [0, 1].
%  TXFUN must have at least two values.
%
%
%  For the 'neg', 'gamma', 'stretch' and 'specified' transformations,
%  floating-point input images whose values are outside the range [0, 1]
%  are scaled first using MAT2GRAT. Other images are converted to
%  floating-point using TOFLOAT. for the 'log' transformation,
%  floating-point images are transformed without being scaled; Other
%  images are converted to floating-point first using TOFLOAT.
%
%
%  The output is of the same class as the input, except if a
%  different class is specified for the 'log' option.
%%
%  Based on Rafael C.Gonzalez, Richard E. Woods, Steven L. Eddins
%  Digital Image Processing Using MATLAB,Second Edition
%  Mender:Hua.Lin
%  Email:h_lin95@163
%  Version: 1.0
transform和convert的区别
%  Date: 2015/08/27
%%
% Verify the correct number of inputs.
narginchk(2, 4)
if strcmp(method,'log')
%  The log transform handles image classes differently than the other
%  transform, so let the LOGTRANSFORM function handles that and then
%  return.
g=logtransform(f,varargin{:});
return;
end;
%  If f is floating point, check to see if it is in the range [0,1].
%  If it is not, force it to be using function mat2gray.
if isfloat(f) && (max(f(:))>1 || min(f(:))<0)
f=mat2gray(f);
end;
%  Store the class of the input for use later.
[ f, revertClass ] = tofloat( f );
%  Perform the intensity transformation specified.
switch method
case 'neg'
g = imcomplement(f);
case 'gamma'
g = gammaTransform(f,varargin{:});
case 'stretch'
g = stretchTransform( f, varargin{:});
case 'specified'
g = specifiedTransform(f,varargin{:});
otherwise
error('Unknown enhancement method.');
end
% Convert to the class of the input image.
g = revertClass(g);
function g = logTransform( f, varargin )
%  G = INTRANS(F, 'log', C, CLASS) computes C*log(1 + F) and
%  multiplies the result by (positive) constant C. If the last two
%  parameters are omitted, C defaults to1. Because the log is used %  frequently to display Fourier spectra, parameter CLASS offers the %  option to specify the class of the output as 'uint8' or
%  'uint16'. If parameter CLASS is omitted, the output is of the
%  same class as the input.
%%
%  Based on Rafael C.Gonzalez, Richard E. Woods, Steven L. Eddins %  Digital Image Processing Using MATLAB,Second Edition
%  Mender:Hua.Lin
%  Email:h_lin95@163
%  Version: 1.0
%  Date: 2015/08/27
%%
[f, revertClass] = tofloat(f);
if num1(varargin) >= 2
if strcmp(varargin{2}, 'unit8')
revertClass = @im2unit8;
elseif strcmp(varargin{2}, 'unit16')
revertClass = @im2unit16;
else
error('Unsupported CLASS option for ''log'' method.');
end;
elseif num1(varargin) < 1
%  Set default for C.
C = 1;
else
C = varargin{1};
end;
g = C*(log(1 + f));
g = revertClass(g);
end
“
function g = specifiedTransform(f,txfun)
% G = INTRANS(F, ‘specified’, TXFUN) performs the intensity
% transformation s = TXFUN(r) where r are input intensities, s are
% output intensities, and TXFUN is an insensity transformation (mapping) % function, expressed as a vector with values in the range [0, 1].
% TXFUN must have at least two values.
% f is floating point with values in the range [0, 1].
%%
% Based on Rafael C.Gonzalez, Richard E. Woods, Steven L. Eddins
% Digital Image Processing Using MATLAB,Second Edition
% Mender:Hua.Lin
% Email:h_lin95@163
% Version: 1.0
% Date: 2015/08/27
%%
txfun = txfun(:);
if any(txfun) > 1 || any(txfun) < 0
error(‘All elements of txfun must be in the range [0, 1].’);
end;
T = txfun;
X = linspace(0, 1, nume1(T));
g = interp1(X, T, f);
end`
function g = stretchTransform( f, varargin )
% G = INTRANS(F, ‘stretch’, M, E) computes a contrast-stretching
% transformation using the expression 1./(1 + (M./(F +
% eps)).^E). Parameter M must be in the range [0, 1]. The default
% value for M is mean2(im2double(F)), and the default value for E
% is 4.
%%
% Based on Rafael C.Gonzalez, Richard E. Woods, Steven L. Eddins
% Digital Image Processing Using MATLAB,Second Edition
% Mender:Hua.Lin
% Email:h_lin95@163
% Version: 1.0
% Date: 2015/08/27
%%
if length(varargin) == 1
% Use defaults.
m = mean2(f);
E = 4.0;
elseif length(varargin) == 3
m = varargin{2};
E = varargin{3};
else error(‘Incorrect number of inputs for the stretch method.’)
end
g = 1./(1 + (m./f).^E);
end`
function g = gammaTransform(f,gamma)
% G = INTRANS(F, ‘gamma’, GAM) performs a gamma transformation on
% the input image using parameter GAM (a required input).
%%
% Based on Rafael C.Gonzalez, Richard E. Woods, Steven L. Eddins
% Digital Image Processing Using MATLAB,Second Edition
% Mender:Hua.Lin
% Email:h_lin95@163
% Version: 1.0
% Date: 2015/08/27
%%
g = imadjust(f, [], [], gamma);
end
function [ outImage, revertClass ] = tofloat( inImage )
% TOFLOAT convert image to floating point.
% [OUTIMAGE, REVERTCLASS] = TOFLOAT(INIMAGE) converts the input image % inImage to floating-point. If inImage is a double or single image, then
% outImage equals inImage. Otherwise, outImage equals IM2SINGLE(IN).
% REVERTCLASS is a function handle that can be used to convert back to the % class of inImage.
%%
% Based on Rafael C.Gonzalez, Richard E. Woods, Steven L. Eddins
% Digital Image Processing Using MATLAB,Second Edition
% Mender:Hua.Lin
% Email:h_lin95@163
% Version: 1.0
% Date: 2015/08/27
%%
identity = @(x) x;
tosingle = @im2single;
table = {‘uint8’, tosingle, @im2uint8
‘uint16’, tosingle, @im2uint16
‘int16’, tosingle, @im2int16
‘logical’, tosingle, @logical
‘double’, identity, identity
‘single’, identity, identity};
classIndex = find(strcmp(class(inImage), table(:, 1)));
if isempty(classIndex)
error(‘Unsupported input image class.’);
end
outImage = table{classIndex, 2}(inImage);
revertClass = table{classIndex, 3};
end
“`

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