File: impath.ps

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%    Copyright (C) 1992, 1996 Aladdin Enterprises.  All rights reserved.
% 
% This software is provided AS-IS with no warranty, either express or
% implied.
% 
% This software is distributed under license and may not be copied,
% modified or distributed except as expressly authorized under the terms
% of the license contained in the file LICENSE in this distribution.
% 
% For more information about licensing, please refer to
% http://www.ghostscript.com/licensing/. For information on
% commercial licensing, go to http://www.artifex.com/licensing/ or
% contact Artifex Software, Inc., 101 Lucas Valley Road #110,
% San Rafael, CA  94903, U.S.A., +1(415)492-9861.

% $Id: impath.ps 6300 2005-12-28 19:56:24Z giles $
% impath.ps
% Reverse-rasterize a bitmap to produce a Type 1 outline.
% (This was formerly a Ghostscript operator implemented in C.)

%	<image> <width> <height> <wx> <wy> <ox> <oy> <string>
%	  type1imagepath <substring>
%		Converts an image (bitmap) description of a character into
%		  a scalable description in Adobe Type 1 format.  The
%		  current transformation matrix should be the same as the
%		  FontMatrix of the font in which this character will be
%		  used: this establishes the scaling relationship between
%		  image pixels (the image is assumed to be 1 unit high in
%		  user space) and the character coordinate system used in
%		  the scalable description.  wx and wy are the character
%		  width, and ox and oy are the character origin relative
%		  to the lower left corner of the bitmap, in *pixels*.
%		The image is assumed to be stored in left-to-right,
%		  top-to-bottom order.  Note that this is not consistent
%		  with the `image' operator's interpretation of the CTM.
%		All coordinates in the scalable description are rounded to
%		  integers, so the coefficients in the FontMatrix should
%		  be on the order of 1/N for some value of N that is
%		  either a multiple of the height/width or is large
%		  compared to the width and height.  (There is a
%		  convention, which some PostScript programs rely on, that
%		  N=1000.)
%		Note that the encoded description has *not* been subjected
%		  to CharString encryption, which is necessary before the
%		  description can be given to type1addpath: to do this,
%		  follow the type1imagepath with
%			4330 exch dup .type1encrypt exch pop
%		If the description is too complex to fit into the supplied
%		  string, a limitcheck error results.  A good rule of
%		  thumb is that the size of the string should be about 6
%		  times the number of 1-bits in the image that are not
%		  completely surrounded by other 1-bits.

% Import the Type 1 opcodes.
(type1ops.ps) runlibfile

100 dict
dup /type1imagepath_dict exch def
begin

/rc { round cvi } bind def
/moving [/rmoveto /hmoveto /vmoveto] def
/drawing [/rlineto /hlineto /vlineto] def

% Convert the current path to a Type 1 token array.
/putxy			% x y ops -> cs_elements
 { 3 -1 roll dup x sub rc exch /x exch def
   3 -1 roll dup y sub rc exch /y exch def
   % stack: ops dx dy
   dup 0 eq
    { % dy = 0, use hmoveto/lineto
      pop exch 1 get
    }
    { 1 index 0 eq
       { % dx = 0, use vmoveto/lineto
         exch pop exch 2 get
       }
       { % use rmoveto/rlineto
         3 -1 roll 0 get
       }
      ifelse
    }
   ifelse
 } bind def
/pathtotype1		% -> charstack
 { 3 dict begin /x 0 def /y 0 def
   mark
   { moving putxy
   }
   { drawing putxy
   }
   { % Convert curve to relative form
     x y 3
      { exch neg 7 index add rc
	exch neg 6 index add rc
	8 -2 roll
      }
     repeat /y exch def /x exch def
     1 index 0 eq 5 index 0 eq and	% dy1=dx3=0, hv
      { 5 -1 roll pop exch pop /hvcurveto
      }
      { dup 0 eq 6 index 0 eq and	% dx1=dy3=0, vh
         { 6 -1 roll pop pop /vhcurveto
	 }
	 { /rrcurveto			% none of the above
	 }
	ifelse
      }
     ifelse
   }
   { /closepath
   }
   pathforall end
 } bind def

end	% type1imagepath_dict

% The main program
/type1imagepath		% image width height wx wy ox oy string ->
			% substring
 { type1imagepath_dict begin
   /tsave save def
   /ostring exch def
   /oy exch def   /ox exch def
   /wy exch def   /wx exch def
   /height exch def   /width exch def
   /data exch def

   /ofilter ostring /NullEncode filter def
   /raster width 7 add 8 idiv def

% Construct the coordinate transformation.
   height dup scale
     matrix currentmatrix matrix invertmatrix setmatrix

% Determine the left side bearing.
   /lsbx width
   0 1 width 1 sub
    { dup dup 8 idiv 0 exch
      raster raster height mul 1 sub
       { data exch get or }
      for exch 8 mod bitshift 128 and 0 ne
       { exch pop exit }
      if pop
    }
   for def

% Compute and encode the origin, width, and side bearing.
   mark
   ox oy dtransform
     rc /opty exch def   rc /optx exch def
   wx wy dtransform
     rc /iwy exch def	rc /iwx exch def
   lsbx ox sub 0 dtransform
     rc /ilsby exch def   rc /ilsbx exch def
   ilsbx
   iwy 0 ne ilsby 0 ne or
    { ilsby iwx iwy /sbw }
    { iwx /hsbw }
   ifelse
   ofilter charstack_write

% Flip over the Y axis, because the image is stored top-to-bottom.
   [1 0 0 -1 0 height] concat
% Account for the character origin.
   lsbx oy translate
% Trace the outline.
   newpath
   width height data .imagepath
   gsave matrix setmatrix pathtotype1 grestore
   ofilter charstack_write
% Terminate the output
   mark /endchar ofilter charstack_write

   ofilter .fileposition ofilter closefile	% flush buffers
   ostring 0 3 -1 roll getinterval
   tsave restore
   end
 } bind def