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%%% Generate a multiresolution variable-contrast grating in order to test contrast sensitivity function
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%%% (c) Pietro Perona, California Institute of Technology. January 21, 2002


%%% Parameters of display being used
DISPLAY.COLS = 1024;
DISPLAY.ROWS = 768;
GRATING.PERIOD = [3 200];
GRATING.CONTRAST = [0.002 1];

%% Create the grating

%% Vertical component
M = log(GRATING.CONTRAST(2));
m = log(GRATING.CONTRAST(1));
DC = (M-m)/(DISPLAY.ROWS-1); %% Contrast increment
IY = exp([m:DC:M]');
figure(1); plot(IY);

%% Horizontal component
m = log(1/GRATING.PERIOD(2));
M = log(1/GRATING.PERIOD(1));
DP = (M-m)/(DISPLAY.COLS-1); %% Period increment
P = exp(m:DP:M);
IX = sin([1:DISPLAY.COLS].*P);
figure(2); plot(IX);
figure(3); plot(P)

%% Final image
I = 1/2 + (1-IY*ones(1,DISPLAY.COLS))/2 + IY * IX /2;
figure(4); image(256*I); colormap(gray(256));
imwrite(I,'grating.jpg','jpg');