/usr/share/psychtoolbox-3/PsychGamma/ComputeGammaExtP.m is in psychtoolbox-3-common 3.0.11.20140816.dfsg1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 | function output = ComputeGammaExpP(x,input)
% output = ComputeGammaExpP(x,input)
%
% Compute the gamma table using an extended power function.
% See Brainard, Pelli, & Robson (2001).
%
% Largest value in input must be the maximum device
% setting. This is wise during measurements in
% any case.
%
% 9/21/93 dhb,ccc Added checks for parameter bounds.
% 10/3/93 dhb,jms Normalize output to max of 1.
% Better be sure that last value is max setting.
% 8/7/00 dhb Rewrote equation this uses completely.
thePow = x(1);
theOffset = x(2);
maxInput = max(input);
minPow = 1e-5;
if (thePow < minPow)
thePow = minPow;
end
if (theOffset < 0)
theOffset = 0;
end
if (theOffset > maxInput)
theOffset = maxInput;
end
output = zeros(size(input));
index = find(input > theOffset);
if (~isempty(index))
output(index) = ((input(index)-theOffset)/(maxInput-theOffset)).^thePow;
end
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