簡單的灰度影象可以通過

InbertIm('example.jpg');

實現灰度翻轉，簡單說就是白變黑，黑變白。

可以自動偵測影象bit數，還有灰度範圍。  

function [invIm]=InvertIm(im, varargin)

% InvertIm generalized image inversion (grayscale reversal)

%    invIm=InvertIm(im) inverts an image array im in the sense of reversing

%    its grayscale (NOT matrix inversion).  InvertIm effects the inversion

%    by computing new image data rather than by reversing the colormap or

%    look-up-table (LUT), which is often, but not always, a better

%    approach.  im can be an array of any dimension composed of numeric or

%    binary elements (integers [uint8, int8, uint16, int16, etc.], floating

%    point [double or single], or logical).  The result invIm is the same

%    data class as im.

%    

%    For numeric arrays, the inverse is computed using 

%

%       invIm = (maxVal + minVal) - im

%

%    with appropriate treatment of the different data types.  For integer

%    arrays, minVal and maxVal are the minimum and maximum allowed

%    integers.  For floating point arrays, if the image data lie within the

%    range [0,1], the inversion is performed with default minVal and maxVal

%    of 0 and 1.  If the image data lie outside [0,1], then the minimum and

%    maxmimum values of the data are used for minVal and maxVal.

%

%    Invert(im, bitsStored) returns the inverse of the image im using a

%    maxVal of 2^bitsStored.  This option is convenient when inverting

%    images with a limited dynamic range, e.g., when you have a 16-bit

%    image that only uses the first 12 bits of data.  This option is only

%    applicable to integer data.

%

%    invIm=Invert(im, [], lowerLimit) returns the inverse of the image im

%    using a minVal of lowerLimit.  This option is useful, for example,

%    when inverting signed integer image data that is only positive.

%

%    invIm=Invert(im, [], [], upperLimit) returns the inverse of the image

%    im using a maxVal of upperLimit.

% 

%    All three optional arguments may be used together (e.g.,

%    invIm=Invert(im, bitsStored, lowerLimit, upperLimit)), but upperLimit

%    will supercede bitsStored.

%

%

%    Example:

%      im=imread('cameraman.tif');  % Brigg's field at MIT

%      fig=figure; colormap(gray)

%      subplot(2,2,1)

%      subimage(im)

%      axis off

%      subplot(2,2,2)

%      imhist(im)

%      ylabel('Number of Pixels')

%

%      invIm=InvertIm(im);

%      subplot(2,2,3)

%      subimage(invIm)

%      axis off

%      subplot(2,2,4)

%      imhist(invIm)

%      ylabel('Number of Pixels')

%

%

%    See also colormap

%    Written by Stead Kiger, Ph.D.

%               Department of Radiation Oncology

%               Beth Israel Deaconess Medical Center

%               Harvard Medical School

%               Boston, MA  02215

%

%    Last revised on April 11, 2007

% Initialize parameters

bitsStored=[];

lowerLimit=[];

upperLimit=[];

% Assign and check optional arguments for parameters

error(nargchk(1, 4, nargin, 'struct'))

% bitsStored

if nargin >= 2,

    bitsStored=varargin{1};

    if ~(isnumeric(bitsStored) || isempty(bitsStored)),

        error('Optional argument bitsStored must be either numeric or empty.')

    end

end

% lowerLimit

if nargin >= 3,

    lowerLimit=varargin{2};

    if ~(isnumeric(lowerLimit) || isempty(lowerLimit)),

        error('Optional argument lowerLimit must be either numeric or empty.')

    end

end

% upperLimit

if nargin == 4,

    upperLimit=varargin{3};

    if ~(isnumeric(upperLimit) || isempty(upperLimit)),

        error('Optional argument upperLimit must be either numeric or empty.')

    end

end

% Check that the image array is either numeric or logical

if ~(islogical(im) || isnumeric(im)),

    error('Input array must be logical or numeric, but is %s',class(im))

end

if islogical(im),

    % logical - just apply not

    invIm=~im;

else

    % determine the image class, i.e., data type; e.g., uint8, int16 etc.

    imClass=class(im);

    % create the function handle for casting the double precision image back

    % into its original class

    clsHdl=str2func(imClass);

    if isinteger(im),

        % get the minimum integer

        minVal=double(intmin(imClass));

        if ~isempty(lowerLimit),

            minVal=double(max(minVal, lowerLimit));

        end

        % get the maximum integer

        maxVal=double(intmax(imClass));

        if ~isempty(bitsStored),

            maxVal=double(min(maxVal, 2^bitsStored - 1));

        end

        if ~isempty(upperLimit),

            maxVal=min(maxVal, upperLimit);

        end

    elseif isfloat(im)

        imMin=min(im(:));

        imMax=max(im(:));

        if imMin >= 0 && imMax <= 1,

            % Intensity image or RGB

            minVal=0;

            maxVal=1;

        else

            minVal=imMin;

            maxVal=imMax;

        end

        if ~isempty(lowerLimit),

            minVal=lowerLimit;

        end

        if ~isempty(upperLimit),

            maxVal=upperLimit;

        end

    else

        error('Input array must be logical or numeric, but is %s',class(im))

    end

    % Compute the inverse and cast the array back into its original class

    invIm = feval(clsHdl, (maxVal + minVal) - double(im));

end