11c0
%! screencomp.ps
%  a program to compare graytone rendering at several different
%  halftone screen frequencies
%  munged from previously posted work, notably that of:
%       From: cplai@daisy.UUCP (Chung-Pang Lai)
%       Subject: halftone parameters
%       Message-ID: <3143@daisy.UUCP>
%       Date: 10 Jul 89 19:47:21 GMT
%       Organization: Daisy Systems, Mt. View, CA

%  This program hacked by Ishmael J. Stefanov-Wagner, eplunix!ijs
%  Eaton-Peabody Laboratory, Boston, MA   May, 1992
%  comment out ShowPrinterParams call if it hangs your printer
%       works on LW, LWIINTX; fails on IIg   Why?

14 dict begin       % set up local dictionary

/ShowPrinterParams {
serverdict begin                % no matching end
statusdict begin
        200 50 moveto
        (Printer Name is ) show
        (                       ) printername show
        200 37 moveto
        pagecount 10 string cvs show ( Copies printed) show
        flush
end
end
} bind def

% define variables to draw the stripes
/str 20 string def  % tmp string holder

/DataString 256 string def

/strip {    % screen => -    draw a graduated gray bar
    /scrfreq exch def

    gsave
    0 -12 moveto
    scrfreq str cvs show
    ( screen) show
        256 1 8 [256 0 0 1 0 0] { DataString }
        700 72 scale image grestore
        newpath 0 setlinewidth 0 setgray 701 0 moveto 0 36 rlineto stroke
} bind def

/page { % draw a page of halftoned graduated bars

    currentscreen       % get default setting
    % stack :  freq angle spot-func
    3 1 roll    % stack : spot-func freq angle
    3 1 roll    % stack : angle spot-func freq
                % divide it with change fctr
    dup /freq exch def  % save a copy for display
    3 1 roll    % stack : freq angle spot-func  
        pop pop pop

    36 0 translate

ShowPrinterParams  % breaks badly on a IIg via Gatorbox

gsave
350 24 translate 24 24 scale 1 1 8 [1 0 0 1 0 0] { (\000) } image grestore

gsave
400 24 translate 24 24 scale 1 1 8 [1 0 0 1 0 0] { (\100) } image grestore

gsave
450 24 translate 24 24 scale 1 1 8 [1 0 0 1 0 0] { (\200) } image grestore

gsave
500 24 translate 24 24 scale 1 1 8 [1 0 0 1 0 0] { (\300) } image grestore

gsave
550 24 translate
        0 setlinewidth
        0 0 moveto 0 24 lineto 24 24 lineto 24 0 lineto closepath stroke
24 24 scale 1 1 8 [1 0 0 1 0 0] { (\377) } image
grestore

    0 50 moveto
    (Default Screen: ) show
    freq str cvs show

    0 100 translate
    freq strip    % draw a strip with default screen

    currentscreen       % get default setting
    % stack :  freq angle spot-func
    3 1 roll    % stack : spot-func freq angle
    3 1 roll    % stack : angle spot-func freq
    pop 100            % divide it with change fctr
    dup /freq exch def  % save a copy for display
    3 1 roll    % stack : freq angle spot-func  
    setscreen
    0 100 translate
    freq strip    % draw a strip with 10 overlapping boxes

    currentscreen       % get default setting
    % stack :  freq angle spot-func
    3 1 roll    % stack : spot-func freq angle
    3 1 roll    % stack : angle spot-func freq
    pop 75            % divide it with change fctr
    dup /freq exch def  % save a copy for display
    3 1 roll    % stack : freq angle spot-func  
    setscreen
    0 100 translate
    freq strip

    currentscreen       % get default setting
    % stack :  freq angle spot-func
    3 1 roll    % stack : spot-func freq angle
    3 1 roll    % stack : angle spot-func freq
    pop 60            % divide it with change fctr
    dup /freq exch def  % save a copy for display
    3 1 roll    % stack : freq angle spot-func  
    setscreen
    0 100 translate
    freq strip

    currentscreen       % get default setting
    % stack :  freq angle spot-func
    3 1 roll    % stack : spot-func freq angle
    3 1 roll    % stack : angle spot-func freq
    pop 45            % divide it with change fctr
    dup /freq exch def  % save a copy for display
    3 1 roll    % stack : freq angle spot-func  
    setscreen
    0 100 translate
    freq strip

    showpage

} bind def

% end of prolog

0 1 255 { DataString exch dup put } bind for  % fill gray data array

/Times-Roman findfont 12 scalefont setfont

0 792 translate
-90 rotate

% 90 rotate                     % feed paper round the other way
% 0 -612 translate              % to see if the tones match (Ha! :-( )

page

end
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