/usr/share/psychtoolbox-3/PsychGamma/InvertGammaExtP.m is in psychtoolbox-3-common 3.0.9+svn2579.dfsg1-1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | function input = InvertGammaExpP(x,maxInput,output)
% output = InvertGammaExpP(x,input)
%
% Invert the gamma table using an extended power function.
% See Brainard, Pelli, & Robson (2001).
%
% Parameter x are the function parameters as returned
% by FitGamma/FitGammaExtP. See ComputeGammaExtP.
%
% Parameter maxInput is the maximum device input
% value (typically 1).
%
% 8/7/00 dhb Wrote it.
% 6/5/10 dhb Update for OS/X assumption of input values as real's in [0-1]
thePow = x(1);
theOffset = x(2);
input = ((maxInput-theOffset)*(output.^(1/thePow))) + theOffset;
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