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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 to 1. 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 % is 4. % 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. % Verify the correct number of inputs. error(nargchk(2, 4, nargin)) 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 [ f, revertClass ] = tofloat( f );% Store the class of f for use later. % 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= gammaTransform(f, gamma) g =imadjust(f,[ ],[ ], gamma); %% function g=stretchTransform(f, varargin) if isempty(varargin) % Use defaults m= mean2(f); E=4.0; elseif length(varargin)==2 m= varargin{1}; E= varargin{2}; else error( 'Incorrect number of inputs for the stretch method.') end g=1./(1+(m./f).^E); %% function g= spcfiedTransform(f, txfun) % f is floating point with values in the range [0 11. txfun= txfun(:);%Force it to be a column vector if any(txfun)> 1 || any(txfun) <= o error('All elements of txfun nust be in the range 10 11.') end T=txfun; x=linspace(0, 1, numel(T))'; g= interp1(X, T, f); %% function g= logTransform(f, varargin) [f, revertclass]= tofloat (f); if numel(varargin)>=2 if strcmp(varargin(2),'uint8') revertclass=@im2uint8 elseif strcmp(varargin{2},'uint16') revertclass = @im2uint16; else error('Unsupported CLASS option for''log'' method.') end end if numel(varargin)< 1 % Set default for C C=1 else C= varargin{1}; end g= C*(log(1+f)); g= revertclass(g);