MATLAB | Complement colors in a Binary image

Binary image is a digital image that has only two possible value for each pixel - either 1 or 0, where 0 represents white and 1 represents black. In the complement of a binary image, the image pixel having value zeros become ones and the image pixel having value ones become zeros; i.e white and black color of the image is reversed. Complementing Binary image using MATLAB library function :

% read a Binary Image in MATLAB Environment
img=imread('geeksforgeeks.jpg');

% complement binary image
% using imcomplement() function
comp=imcomplement(img);

% Display Complemented Binary Image 
imshow(comp);

  Complementing Binary image without using library function : We can complement a binary image by subtracting each pixel value from maximum possible pixel value a binary image pixel can have (i.e 1 ), and the difference is used as the pixel value in the complemented image. It means if an image pixel have value 1 then, in complemented binary image same pixel will have value ( 1 - 1 ) = 0 and if Binary image pixel have value 0 then, in complemented binary image same pixel will have value ( 1 - 0 ) = 1. Below is the Implementation of above idea-

% This function will take a Binary image as input
% and will complement the colors in it.

function [complement] = complementBinary(img)
     
    % Determine the number of rows and columns
    % in the binary image array
 
    [x, y]=size(img);
   
    % create a array of same number rows and
    % columns as original binary image array
    complement=zeros(x, y);
    
    % loop to subtract 1 to each pixel.
    for i=1:x
        for j=1:y
              complement(i, j) = 1-img(i, j);
        end
   end
end


%  Driver Code

% read a Binary  Image in MATLAB Environment
img=imread('geeksforgeeks.jpg');

% call complementBinary() function to
% complement colors in the binary Image
comp=complementBinary(img);

% Display complemented Binary image
imshow(result);

  Alternate way : In MATLAB, Arrays are basic data structure.They can be manipulated very easily. For example Array = 1 - Array ; Above code will subtract each element of the array from 1. So, Instead of using two loops to subtract 1 to each pixel of binary image. We can directly write it as - comp=1-img Here 'img' is our binary image array. Below code will also complement a binary Image

% read a Binary Image in MATLAB Environment
img=imread('geeksforgeeks.jpg');

% complement each pixel by subtracting it from  1 
comp=1-img;

% Display Complemented binary Image 
imshow(comp);

Input: Output:   References : https://in.mathworks.com/help/images/ref/imcomplement.html