% octave function loadf.m
%
% loads response function from picture of test chart
%
% returns [black, 11 step greyvalues, white] 
%load in the function f(q)
%from test pattern picture
function [f, y]=loadf(k);
if ((k<100) | (k>118))
  error('must load one of frame 100 to 118')
end%if
%%%Y=loadtestpatterntop(k);
Y=loadframe(k);
Ytop = Y(395:575,494:1531); % top portion of test pattern
Y=Y(395:907,494:1524); % take out only the test pattern portion
y=mean(Ytop);
%%plot(y)
%find(absdiff=abs((diff(y)))>4)
%and edit out repeats:
stepposn=[1 93 188 284 379 472 568 662 756 850 944 1036];
for l=1:11
  begin=stepposn(l);
  endin=stepposn(l+1);
  yportion=y(begin:endin);
  f(l)=median(yportion);
end%for

f=f(11:-1:1); % reverse samples

%%blackregionL=Y(181:331,383:454);
%%blackregionR=Y(181:331,587:659);
blackregionL=Y(181+10:331-10,383:454); % to be sure top and bottom ok
blackregionR=Y(181+10:331-10,587:659);
b1=mean(blackregionL); % mean down cols
b1=median(b1); % median across rows
b2=mean(blackregionR);
b2=median(b2);
black=(b1+b2)/2;

%%keyboard
f=[black;f(:)]; % prepend black to this

%whiteregion=Y(181+10:331-10,454+10:587-10);
%w=mean(whiteregion);
%w=median(w);
%f=[f;w];
%white region appears to be same as lightest test bar

q0=.011; % true black
% true black then 11 values of steps:
q=[.011; .021; .048; .079; .126; .185; .264; .358; .472; .622; .733; .893];

% now make a nice plot
%x=linspace(0,11,length(y));
%grid
%axis([0 12 0 256]);
%xlabel('spatial coordinate, x')
%ylabel('response function, y(x)=f(q(x))')
%plot(x,y)