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%!PS-Adobe-3.0
%
% ********************************************************************************
%
% Figure 7.8(d) from the book: "The Theory of the Moire Phenomenon"
% by I. Amidror, published by Kluwer Academic Publishers, 1999.
%
%		* * *  Copyright (c) 1999 EPFL  * * *
%
% Author: I. Amidror
%
% Modified: June 9, 1999
%
% ********************************************************************************
%
% A latent image in the superposition of 2 line gratings:
%
% The grating parameters are as follows:
% 
% theta1, theta2 - the grating angles, in degrees.
% p1, p2 - the respective grating periods, in deciinches.
% xshifti - the period-shifts for the i-th grating, in terms of period fractions.
% len - the length of each of the gratings, in centiinches.
% wid - the width of each of the gratings, in centiinches.
%
% ********************************************************************************
%


/inch {72 mul} def
/centiinch {0.72 mul} def
0.7 centiinch setlinewidth


/len 170 def		% grating length in centiinches
/wid 120 def		% grating width in centiinches
/len2 len 2 div def
/wid2 wid 2 div def


/starwidth 0.75 inch def
/starwidth2 0.75 inch 2 div def


/starside			% From blue PS book p. 51
{starwidth 0 inch lineto	% add line to path
currentpoint translate		% move origin
120 rotate
} def

/star
{moveto
currentpoint translate
3 {starside} repeat
closepath
} def


/Helvetica findfont
9 scalefont setfont


-1 inch 1.45 inch translate
gsave


% ******************************** Fig. (d):

/theta1 0 def		% angle of grating A
/theta2 0 def		% angle of grating B

/rot 0 def		% general rotation to prevent printer artifacts

/p1 3 def		% period of grating A
/p2 3 def		% period of grating A

/xshift1 0 p1 mul def		% period-shift of grating A (e.g. 0.5)
/xshift2 6.5 p2 mul def		% period-shift of grating B (e.g. 0.5)


% Draw grating A:
gsave
5 inch 6 inch translate
theta1 rot add rotate

gsave
newpath
0 p1 len		% draw lines
{centiinch len2 p1 div round p1 mul xshift1 sub centiinch sub wid2 centiinch neg moveto
0 centiinch wid centiinch rlineto} for
stroke
-0.95 inch -0.6 inch moveto
(A) show

% Make a triangular hole within grating A:
newpath
1 setgray	% white
starwidth2 neg -0.4 inch star fill
grestore

% Fill the triangular hole with a half-period shifted grating:
gsave
/xshift1 0.5 p1 mul def		% period-shift of grating A (e.g. 0.5)
newpath
starwidth2 neg -0.4 inch star clip
starwidth2 0.4 inch translate		% return to initial position before the star

newpath
0 p1 len		% draw lines
{centiinch len2 p1 div round p1 mul xshift1 sub centiinch sub wid2 centiinch neg moveto
0 centiinch wid centiinch rlineto} for
stroke
grestore

grestore



% Draw grating B:
gsave
5 inch 5.8 inch translate
theta2 rot add rotate
newpath
0 p2 len		% draw lines
{centiinch len2 p2 div round p2 mul xshift2 sub centiinch sub wid2 centiinch neg moveto
0 centiinch wid centiinch rlineto} for
stroke
-0.77 inch -0.6 inch moveto
(B) show
grestore


gsave
5 inch 6 inch translate
-0.05 inch -1.08 inch moveto
/Times-Roman findfont
12 scalefont setfont
((d)) show
grestore


gsave
2.75 inch 1 inch translate
0 inch 0 inch moveto
/Times-Bold findfont
12 scalefont setfont
(Figure 7.8(d)) show
/Times-Roman findfont
12 scalefont setfont
( from the book: ) show
/Times-Italic findfont
12 scalefont setfont
(The Theory of the Moire) show
-0.06 inch 0 inch rmoveto
(\302 Phenomenon) show
/Times-Roman findfont
12 scalefont setfont
0 inch -0.25 inch moveto
(    by I. Amidror, published by Kluwer Academic Publishers, 1999.) show
grestore



grestore

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