what is the unwrap2D and ftp functions

`unwrap2D` and `ftp` are custom functions that need to be implemented separately in MATLAB.

`unwrap2D` is a function that performs 2D phase unwrapping. It takes in two phase maps (`phase_map1` and `phase_map2`) and combines them to get the unwrapped phase map. This function is commonly used in FTP to avoid phase wrapping errors.

Here is an example implementation of `unwrap2D` function:

function phase_unwrapped = unwrap2D(phase_map1, phase_map2)
    % Calculate the 2D phase difference
    phase_diff = phase_map1 - phase_map2;

    % Set the center pixel to zero to avoid phase jumps
    phase_diff(floor(size(phase_diff,1)/2)+1, floor(size(phase_diff,2)/2)+1) = 0;

    % Perform 2D phase unwrapping
    phase_unwrapped = unwrap(angle(exp(1i*phase_diff)));

    % Set the center pixel back to zero
    phase_unwrapped(floor(size(phase_unwrapped,1)/2)+1, floor(size(phase_unwrapped,2)/2)+1) = 0;
end

`ftp` is a function that performs Fourier transform profilometry on the unwrapped phase map to obtain the height map. It applies a 2D Fourier transform on the phase map and uses the frequency domain information to extract the height information.

Here is an example implementation of the `ftp` function:

function height_map = ftp(phase_unwrapped)
    % Calculate the Fourier spectrum of the phase map
    F = fft2(phase_unwrapped);

    % Shift the Fourier spectrum to center it
    F = fftshift(F);

    % Calculate the frequency domain coordinates
    [X,Y] = meshgrid(1:size(F,2), 1:size(F,1));
    x = X - size(F,2)/2 - 1;
    y = Y - size(F,1)/2 - 1;

    % Calculate the height map using the inverse Fourier transform
    height_map = ifft2(1i*2*pi*(x.*F + y.*F))./abs(F).^2;

    % Shift the height map to center it
    height_map = fftshift(height_map);
end

Note: These are just example implementations of `unwrap2D` and `ftp` functions and may not be optimized for speed or accuracy.