function res = inversion( N )
    I = imread(N);
    [m, n, can] = size(I);
    res = zeros(m,n);
    if (can > 1)
        I = rgb2gray(I);
    end
    res =255 -I;
    figure
    subplot(1, 2, 1)
    colormap(gray(256))
    imagesc(I);
    subplot(1, 2, 2)
    colormap(gray(256))
    imagesc(res);
    title(strcat(['Image de taille', num2str(m), 'x', num2str(n)]));
end

