/usr/share/psychtoolbox-3/PsychCal/ContrastMatch.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 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 | function weight=ContrastMatch(device,dimWeight,foreColor,backColor)
% weight=ContrastMatch(device,dimWeight,[foreColor],[backColor])
%
% Displays two gratings. The bright grating alternates white and weight*white,
% producing luminances LMax and LBright.
% The dim grating alternates dimWeight*white and black, producing luminances
% LDim and LMin.
% When the grating contrasts match, LMax/LBright=LDim/LMin.
% In a more compact notation, L1/Lb=Ld/L0. We set the weight wd that produces
% Ld, and the observer adjusts the weight wb that produces Lb. They are related
% by the gamma function, y=g(w), where y is the normalized luminance,
% y=(L-L0)/(L1-L0). We know wb and wd, and we have access to the gamma function,
% so we can compute yb and yd. Solving for L, we have
% L=y*(L1-L0)+L0
% Our relation at match can be rewritten as
% L1*L0=Ld*Lb
% 0=Ld*Lb-L1*L0
% =(yd*(L1-L0)+L0)*(yb*(L1-L0)+L0)-L1*L0
% Let's divide by L1^2, and define r=L0/L1.
% =(yd*(1-r)+r)*(yb*(1-r)+r)-r
% This is a quadratic equation in r
% =(yd+(1-yd)*r)*(yb+(1-yb)*r)-r
% =yd*yb+(yb*(1-yd)+yd*(1-yb)-1)*r+(1-yd)*(1-yb)*r^2
% c=[(1-yd)*(1-yb) yb*(1-yd)+yd*(1-yb)-1 yd*yb]; % coefficients of quadratic polynomial
% r=roots(c)
% The answer, r, is the desired ratio of L0/L1.
%
% 5/28/96 dgp Wrote it.
% 5/28/96 dgp Updated to use new GetMouse, that flushes mouse events.
% 8/4/96 dhb Changed name to ContrastMatch.
% 8/16/97 dgp Changed "text" to "theText" to avoid conflict with TEXT function.
% 7/19/98 dgp Removed obsolete TIMER.
% 6/30/03 dgp Updated Screen OpenScreen to Screen OpenWindow.
PsychDefaultSetup(1);
if nargin<2 || nargout>1
error('Usage: weight=GratingMatch(device,dimWeight,[foreColor],[backColor])');
end
if nargin<4
backColor=[0 0 0];
end
if nargin<3
foreColor=[255 255 255];
end
dpi=67;
distanceM=0.57;
pixelDeg=57/(dpi*distanceM/0.0254);
[win, screenRect] = Screen('OpenWindow', device);
screenRect=reshape(screenRect,1,4);
white=[255 255 255];
black=[0 0 0];
clut=(0:255)';
clut=clut(:,[1 1 1]);
clut(1,:)=white;
clut(256,:)=black;
clut(2,:)=black;
clut(3,:)=white;
clut(4,:)=black;
clut(5,:)=dimWeight*white+(1-dimWeight)*black;
Screen('SetClut', win, clut);
if 0
blend=1:RectHeight(barRect);
blend=blend-blendPeriodPix*floor(blend/blendPeriodPix); % modulo the period
blend=2+(blend >= round(forePart*blendPeriodPix));
blend=Expand(blend',RectWidth(barRect),1);
pure=ones(RectHeight(barRect),RectWidth(barRect));
Screen('BlitImage255',blend,barRect);
barRect=OffsetRect(barRect,RectWidth(barRect),0);
Screen('BlitImage255',pure,barRect);
barRect=OffsetRect(barRect,RectWidth(barRect),0);
end
% Create two 1 c/deg squarewave gratings at different luminances.
% CLUT entries: 1=adjustable, 2=foreColor, 3=backColor
barWidth=max(1,round(0.5/(1*pixelDeg))); % 1 c/deg grating
testRect=ScaleRect(screenRect,0.5,0.5);
testRect=round(AlignRect(testRect,screenRect,RectLeft,RectTop));
barRect=SetRect(0,0,barWidth,RectHeight(testRect));
for color=0:2:2
barRect=AlignRect(barRect,testRect,RectLeft,RectBottom);
for i=0:2:ceil(RectWidth(testRect)/RectWidth(barRect))
Screen('FillRect', win, color+1,barRect);
barRect=OffsetRect(barRect,RectWidth(barRect),0);
Screen('FillRect', win, color+2,barRect);
barRect=OffsetRect(barRect,RectWidth(barRect),0);
end
Screen('FillRect', win, 0,AdjoinRect(testRect,testRect,RectRight))
testRect=AdjoinRect(testRect,testRect,RectBottom);
end
% Print instructions
theText=sprintf( 'Move the mouse up and');
theText=char(theText,'down to match the grating');
theText=char(theText,'contrasts. Click when ');
theText=char(theText,'you see one long grating,');
theText=char(theText,'partly occluded by a dark');
theText=char(theText,'filter.');
s=24;
%Screen('TextFont', win, 'Chicago');
Screen('TextSize', win, s);
s=s+8;
% textRect=SetRect(0,0,Screen('TextWidth',theText(2,:)),size(theText,1)*s);
% textRect=CenterRect(textRect,screenRect);
% textRect=OffsetRect(textRect,RectWidth(screenRect)/4+20/4,0);
% for i=1:size(theText,1)
% Screen('DrawText',textRect(RectLeft),textRect(RectTop)+s*i,255,theText(i,:));
% end
DrawFormattedText(win, theText, 0, 'center', 'center', white);
% animate
% track vertical mouse position with vertical slider knob.
sliderRect=SetRect(0,0,20,RectHeight(screenRect));
sliderRect=CenterRect(sliderRect,screenRect);
knobRect=SetRect(0,0,RectWidth(sliderRect),RectWidth(sliderRect));
knobRect=InsetRect(CenterRect(knobRect,sliderRect),1,0);
top=RectTop;
bottom=RectBottom;
Screen('FillRect', win, 0, sliderRect);
Screen('FrameRect', win, 255, sliderRect);
while 1
[x,y,button]=GetMouse;
weight=(sliderRect(bottom)-y)/RectHeight(sliderRect);
Screen('SetClut', win, weight*foreColor+(1-weight)*backColor,1);
dy=y-(knobRect(top)+knobRect(bottom))/2;
residue=knobRect;
if dy>0
residue(bottom)=residue(top)+dy;
else
residue(top)=residue(bottom)+dy;
end
knobRect=OffsetRect(knobRect,0,dy);
Screen('FillRect', win, 0,residue);
Screen('FillRect', win, 255,knobRect);
if(button) break; end;
WaitSecs(.01); % make sure we miss some frames, so mouse gets updated
end
Screen('CloseAll');
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