how to create vision contrast test system in MATLAB?

Anyone have any idea how I can create this chart? I am using cosine functions with different frequencies and plotting them over a 2D grid. However, I do not know how to get the exact same contrast as the original chart

x = linspace(- .5 * pi, .5* pi, rows);
y = linspace(1, 100, rows); 
[xx,~] = meshgrid(x, y); 
z = L(i) .* (C(i) .* cos(2 .* pi .* freq .* xx) + 1);

where L is the luminance and C the contrast. If you know a better way, It'd be great to learn it.