/usr/share/psychtoolbox-3/PsychCal/MeasureDpi.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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 | function dpi=MeasureDpi(theScreen)
% dpi=MeasureDpi([theScreen])
% Helps the user to accurately measure the screen's dots per inch.
%
% Denis Pelli
% 5/28/96 dgp Updated to use new GetMouse.
% 3/20/97 dgp Updated.
% 4/2/97 dgp FlushEvents.
% 4/26/97 dhb Got rid of call to disp(7), which was writing '7' to the
% command window and not producing a beep.
% 8/16/97 dgp Changed "text" to "theText" to avoid conflict with TEXT function.
% 4/06/02 awi Check all elements of the new multi-element button vector
% returned by GetMouse on Windows.
% Replaced Chicago font with Arial because it's available on
% both Mac and Windows
% 11/6/06 dgp Updated from PTB-2 to PTB-3.
if nargin>1 || nargout>1
error('Usage: dpi=MeasureDpi(screen)');
end
if nargin<1
theScreen=0;
end
AssertOpenGL;
try
disp('Please find an object of known width to hold against the display.');
disp('E.g. a ruler or an 8.5-inch page.')
inches=input('Do you prefer inches (1) or cm (0)? ');
if inches
unitInches=1;
units='inches'; % e.g. distance in inches
unit='inch'; % e.g. 5 inch object
else
unitInches=1/2.54;
units='cm';
unit='cm';
end
objectInches=input(sprintf('How wide is your object, in %s? ',units))*unitInches;
disp('A small correction will be made for your viewing distance and the thickness of');
disp('the screen''s clear front plate, which separates your object from the screen''s');
disp('light emitting surface.');
if Screen('FrameRate',theScreen)==0
thicknessInches=0.1;
fprintf('The zero nominal frame rate of your display suggests that it''s an LCD, \n');
fprintf('with a thin (%.1f inch) clear front plate.\n',thicknessInches);
else
thicknessInches=0.25;
fprintf('The nonzero nominal frame rate of your display suggests that it''s a CRT, \n');
fprintf('with a thick (%.1f inch) clear front plate.\n',thicknessInches);
end
distanceInches=input(sprintf('What is your viewing distance, roughly, in %s? ',units))*unitInches;
[window,screenRect]=Screen('OpenWindow',theScreen);
white=WhiteIndex(window);
black=BlackIndex(window);
% Instructions
s=sprintf('Hold your %.1f-%s-wide object against the display.',objectInches/unitInches,unit);
theText={s,'Press, drag, and release the mouse to draw a bar'...
,'that matches the width of your object. Use one eye.'};
Screen('TextFont',window,'Arial');
s=24;
Screen('TextSize',window,s);
textLeading=s+8;
textRect=Screen('TextBounds',window,theText{1});
textRect(4)=length(theText)*textLeading;
textRect=CenterRect(textRect,screenRect);
textRect=AlignRect(textRect,screenRect,RectTop);
textRect(RectRight)=screenRect(RectRight);
dragText=theText;
dragTextRect=textRect;
% Animate
% Track horizontal mouse position to draw a bar of variable width.
for i=1:length(dragText)
Screen('DrawText',window,dragText{i},dragTextRect(RectLeft),dragTextRect(RectTop)+textLeading*i,black);
end
barRect=CenterRect(SetRect(0,0,RectWidth(screenRect),20),screenRect);
fullBarRect=barRect;
top=RectTop;
bottom=RectBottom;
left=RectLeft;
right=RectRight;
Screen('FillRect',window,white,barRect);
Screen('FrameRect',window,black,barRect);
Screen('Flip',window);
oldButton=0;
while 1
[x,y,button]=GetMouse;
FlushEvents('mouseDown');
if any(button)
if ~oldButton
origin=x;
barRect(left)=origin;
barRect(right)=origin;
else
if x<origin
barRect(left)=x;
barRect(right)=origin;
else
barRect(left)=origin;
barRect(right)=x;
end
end
if ~IsEmptyRect(barRect)
Screen('FillRect',window,black,barRect);
end
backgroundRect=barRect;
backgroundRect(left)=screenRect(left);
backgroundRect(right)=barRect(left);
if ~IsEmptyRect(backgroundRect)
Screen('FillRect',window,white,backgroundRect);
end
backgroundRect(left)=barRect(right);
backgroundRect(right)=screenRect(right);
if ~IsEmptyRect(backgroundRect)
Screen('FillRect',window,white,backgroundRect);
end
for i=1:length(dragText)
Screen('DrawText',window,dragText{i},dragTextRect(RectLeft),dragTextRect(RectTop)+textLeading*i,black);
end
Screen('FrameRect',window,black,fullBarRect);
Screen('Flip',window);
if ~IsEmptyRect(barRect)
Screen('FillRect',window,black,barRect);
end
else
if oldButton
objectPix=RectWidth(barRect);
dpi=objectPix/objectInches;
dpi=dpi*distanceInches/(distanceInches+thicknessInches);
clear theText
if inches
theText{1}=sprintf('%.0f dots per inch.',dpi);
else
theText{1}=sprintf('%.0f dots per inch. (%.0f dots/cm.)',dpi,dpi/2.54);
end
theText{2}='Click once to do it again; twice if you''re done.';
textRect=Screen('TextBounds',window,theText{2});
textRect(4)=length(theText)*textLeading;
textRect=CenterRect(textRect,screenRect);
textRect=AlignRect(textRect,screenRect,RectTop);
Screen('FillRect',window,white,InsetRect(dragTextRect,0,round(-0.3*textLeading)));
for i=1:length(theText)
Screen('DrawText',window,theText{i},textRect(RectLeft),textRect(RectTop)+textLeading*i,black);
end
Screen('Flip',window);
i=GetClicks;
if ~IsEmptyRect(barRect)
Screen('FillRect',window,white,barRect);
end
Screen('FillRect',window,white,InsetRect(textRect,0,round(-0.3*RectHeight(textRect))));
if i>1
break
end
for i=1:length(dragText)
Screen('DrawText',window,dragText{i},dragTextRect(RectLeft),dragTextRect(RectTop)+textLeading*i,black);
end
Screen('FrameRect',window,black,fullBarRect);
Screen('Flip',window);
end
end
oldButton=any(button);
end
Screen('Close',window);
catch
ShowCursor;
Screen('CloseAll');
FlushEvents('keyDown');
while CharAvail
GetChar;
end
psychrethrow(psychlasterror);
end
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