In MATLAB, a Grayscale image is a 2-D Image array ( M*N ) of color pixel. When we complement colors in a Grayscale image, Each color pixel in grayscale image is replaced with their complementary color pixel.
Dark areas become lighter and light areas become darker in the grayscale image as result of complement.
Complementing colors of a Grayscale Image Using MATLAB Library Function :
Complementing colors of a Grayscale Image without Using MATLAB Library Function :
Grayscale Images have their pixel value in the range 0 to 255. we can complement a grayscale image by subtracting each pixel value from maximum possible pixel value a Grayscale image pixel can have (i.e 255 ), and the difference is used as the pixel value in the complemented Grayscale image.
It means if an image pixel have value 100 then, in complemented Grayscale image same pixel will have value ( 255 – 100 ) = 155.
And if Grayscale image pixel have value 0 then, in complemented grayscale image same pixel will have value ( 255 – 0 ) = 255.
Similarly, if Grayscale image pixel have value 255 then, in complemented grayscale image same pixel will have value ( 255 – 255 ) = 0.
Below is the Implementation of above idea:
Instead of using two loops to subtract 255 to each pixel of grayscale image. We can directly write it as
comp = 255-image. Above code will subtract each value of image array from 255.
Below code will also complement a Grayscale Image: