Can someone explain me this part of array indexing?

I’m trying to manipulate an image with MATLAB, I want to flip the image without the function flip, so I found this, If someone knows how does it work can explain me?

img(:,(end:-1:1),:,:);

>Solution :

Try it yourself, see the example below:

A = 1:10
A(end:-1:1)
A =

     1     2     3     4     5     6     7     8     9    10
ans =

    10     9     8     7     6     5     4     3     2    1   

end is the last element of the array, start:step:end creates an array starting at start, ending at end with step size step. Setting the step negative flips the array. This can be done across all dimensions of an array, so across the second in your case.