function out = gammacon(val,whichway)

%Convert rgb to luminance or vive versa using a gamma function
%values taken on 12/12/2018 in lab 4

%String argument can be either 'rgb2lum' or 'lum2rgb'

a = 3.4590;
b =  128.492;
g = 1.81;

if strcmp('rgb2lum',whichway)
    out = a+b.*(val.^g); 
elseif strcmp('lum2rgb',whichway)
    out = exp(log((val-a)./b)./g);
elseif strcmp('rgb2rgb',whichway)
    out = (a/b)+(val.^g); 
else
    disp('Invalid string input!')
    out = 0;
    return
end

return