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potrace - Transforms bitmaps into vector graphics…  more info»


potrace(1)                                                potrace(1)

       potrace - transform bitmaps into vector graphics.

       potrace [options] [filename...]

       potrace  is  a  utility  for  tracing  a bitmap, which means,
       transforming a bitmap into  a  smooth,  scalable  image.  The
       input  is a bitmap, which means, a pixel-based image composed
       of the two colors black and white only. The default output is
       an  encapsulated  PostScript  file (EPS). A typical use is to
       create EPS files from scanned data, such as company  or  uni‐
       versity logos, handwritten notes, etc. The resulting image is
       not "jaggy" like a bitmap, but smooth. It can  then  be  ren‐
       dered at any resolution.

       potrace  can read bitmaps in the following formats: PBM, PGM,
       PPM (collectively known as PNM, see pnm(5)), as well  as  BMP
       (Windows  and  OS/2  bitmap  formats). The input image should
       only use the two colors black and white. If other pixel  val‐
       ues  appear in the input, they will be converted to black and
       white using a simple threshold method.

       potrace can currently produce the following  output  formats:
       EPS,  PostScript,  PDF,  SVG,  PGM, and XFIG. An experimental
       gimppath backend is also available. Additional backends might
       be added in the future.

       The following options are supported. Dimensions (arguments of
       type dim) can have optional units, e.g. 6.5in,  15cm,  100pt.
       The  default unit is inches (or centimeters, if this was con‐
       figured at  compile  time,  see  COMPILE  TIME  CONFIGURATION
       below).  For pixel-based output formats such as PGM and gimp‐
       path, the default unit is pixels.

   General options:
       -h, --help     print help message and exit.

       -v, --version  print version info and exit.

       -l, --license  print license info and exit.

       -V, --show-defaults
                      print the defaults which  were  compiled  into
                      this version of potrace, and exit.

       --progress     display a progress bar for each bitmap that is
                      processed. This is useful for interactive use,
                      and  requires a terminal. The default behavior
                      is not to show any progress information.

   Input/output options:
       filename       If filename arguments are given, then  potrace
                      will  by  default  create  one output file for
                      each input filename given.  The  name  of  the
                      output  file  is obtained from the input file‐
                      name by changing its suffix according  to  the
                      chosen  backend.  If  changing  the  suffix is
                      impossible because the names of the input  and
                      output files would be identical, then the out‐
                      put filename is created by adding  the  "-out"
                      suffix  to  the  name of the input file. If no
                      filename arguments  are  given,  then  potrace
                      acts  as a filter, reading from standard input
                      and writing to standard output. A filename  of
                      "-" may be given to specify reading from stan‐
                      dard input.

       -o filename, --output filename
                      write output  to  this  file.  All  output  is
                      directed to the specified file. If this option
                      is used, then  multiple  input  filenames  are
                      allowed only for those backends which can han‐
                      dle multiple bitmaps; these are currently  the
                      PostScript  and  PGM  backends.  In this case,
                      each input file may contain one or  more  bit‐
                      maps,  and  all the bitmaps from all the input
                      files are processed and  the  output  concate‐
                      nated  into  a  single file. A filename of "-"
                      may be given to specify  writing  to  standard

   Backend selection:
       -b name, --backend name
                      Select  backend  by name, where name is one of
                      eps, postscript, ps, pdf, svg, pgm,  gimppath,
                      xfig.  Backend  names can be abbreviated by an
                      unambiguous prefix.

       -e, --eps      Encapsulated PostScript backend (default). The
                      input  is  a  single  bitmap;  the output is a
                      stand-alone,  encapsulated   PostScript   file
                      which can be included in other documents.

       -p, --postscript
                      PostScript  backend.  For  this  backend,  the
                      input may  consist  of  multiple  concatenated
                      bitmaps,  which  will  be turned into a multi-
                      page PostScript document.

       -b pdf, --backend pdf
                      PDF backend. For this backend, the  input  may
                      consist   of  multiple  concatenated  bitmaps,
                      which will be turned  into  a  multi-page  PDF
                      document.  Rotation  (option  -A)  is  not yet
                      implemented for this backend.

       -s, --svg      SVG backend. This backend produces a  scalable
                      vector  graphics  (SVG) file. This backend can
                      process one bitmap per output file.

       -g, --pgm      PGM backend. This backend produces a  portable
                      greymap (PGM) file. It is a convenient backend
                      for antialiasing a bitmap image. The input may
                      consist  of  multiple concatenated bitmaps, in
                      which case multiple greymaps will  be  written
                      to the output.

       -b gimppath, --backend gimppath
                      Experimental  gimppath  backend.  This backend
                      produces a path which can be imported  by  the
                      GNU  Image Manipulation Program (Gimp) (in the
                      Layers, Channels & Paths dialog, select Paths,
                      then right-click and select Import Path). Note
                      that Gimp's paths have some peculiar features:
                      they  have  no  bounding  box,  they cannot be
                      scaled, and all control points are  forced  to
                      be  integers.  For these reasons, it is diffi‐
                      cult to produce good Gimp paths at low resolu‐
                      tions. The gimppath backend ignores almost all
                      scaling and placement  options;  instead,  the
                      --unit  option must be used to set the desired
                      magnification. The  --rotate  option  is  also
                      recognized.  Note  that  the imported path can
                      lie outside the bounds of the current image in
                      Gimp; in this case, one needs to move the path
                      (alt-click) or work with a larger image.

       -b xfig, --backend xfig
                      XFig backend. Note that  XFig  uses  X-splines
                      instead  of Bezier curves, thus it is not pos‐
                      sible to translate the output of potrace  into
                      the  XFig  format with absolute accuracy. This
                      backend does a reasonable approximation  using
                      two  control points for each Bezier curve seg‐
                      ment. Note that the -u option  has  no  effect
                      for this backend, as control points are always
                      rounded to the nearest 1/1200 of  an  inch  in
                      XFig.  Rotation  and  color  are  implemented.
                      Curve optimization is disabled.

   Algorithm options:
       For more detailed information on these options, see TECHNICAL
       DOCUMENTATION below.

       -z policy, --turnpolicy policy
                      specify  how  to  resolve  ambiguities in path
                      decomposition. Must be one  of  black,  white,
                      right,  left,  minority,  majority, or random.
                      Default is  minority.  Turn  policies  can  be
                      abbreviated by an unambigous prefix, e.g., one
                      can specify min instead of minority.

       -t n, --turdsize n
                      suppress speckles of up to this many pixels.

       -a n, --alphamax n
                      set  the  corner  threshold   parameter.   The
                      default  value  is  1. The smaller this value,
                      the more sharp corners will  be  produced.  If
                      this  parameter is negative, then no smoothing
                      will be performed and the output is a polygon.
                      The  largest  useful  value  is  4/3 or 1.334,
                      which suppresses all corners and leads to com‐
                      pletely smooth output.

       -n, --longcurve
                      turn  off curve optimization. Normally potrace
                      tries to join adjacent Bezier  curve  segments
                      when  this  is  possible. This option disables
                      this behavior,  resulting  in  a  larger  file

       -O n, --opttolerance n
                      set  the  curve  optimization  tolerance.  The
                      default value is 0.2. Larger values allow more
                      consecutive Bezier curve segments to be joined
                      together in a single segment, at  the  expense
                      of accuracy.

       -u n, --unit n set  output  quantization.  Coordinates in the
                      output  are  rounded  to  1/unit  pixels.  The
                      default  of 10 usually gives good results. For
                      some of the debug modes, a value of 100  gives
                      more accurate output. In the case of the gimp‐
                      path backend, the -u option is used to set the
                      desired  magnification.  This  option  has  no
                      effect for the XFig backend, which always ras‐
                      terizes to 1/1200 inch.

       -d n, --debug n
                      produce  debugging  output of type n. This has
                      different effects for different backends.  For
                      the   PostScript/EPS   backends,   the  values
                      n=1,2,3 illustrate the intermediate stages  of
                      the potrace algorithm.

   Scaling and placement options:
       -W dim, --width dim
                      set  the width of output image. If only one of
                      width and height is specified,  the  other  is
                      adjusted  accordingly so that the aspect ratio
                      is preserved.

       -H dim, --height dim
                      set the height of output  image.  See  -W  for

       -r n[xn], --resolution n[xn]
                      set  the  resolution (in dpi). One inch in the
                      output image corresponds to this  many  pixels
                      in  the  input.  Note  that  it follows that a
                      larger  value  results  in  a  smaller  output
                      image.  It  is  possible  to specify different
                      resolutions in the x and y directions by  giv‐
                      ing  an argument of the form nxn.  This option
                      has no effect for the PGM backend.

       -x n[xn], --scale n[xn]
                      set the scaling factor (PGM backend  only).  A
                      value  greater  than  1 enlarges the output, a
                      value  between  0  and  1  makes  the   output
                      smaller.  It  is possible to specify different
                      scaling factors in the x and y  directions  by
                      giving an argument of the form nxn.

       -S n, --stretch n
                      set  the  aspect ratio. A value greater than 1
                      means the image will be  stretched  in  the  y
                      direction.  A  value between 0 and 1 means the
                      image will be stretched in the x direction.

       -A angle, --rotate angle
                      set the rotation angle (in degrees). The  out‐
                      put  will  be rotated counterclockwise by this
                      angle. This is  useful  for  compensating  for
                      images that were scanned not quite upright.

       -M dim, --margin dim
                      set  all  four  margins.  The  effect  of this
                      depends on  the  backend.  For  variable-sized
                      backends  (EPS,  PGM,  SVG),  the margins will
                      simply be added around the  output  image  (or
                      subtracted,  in case of negative margins). For
                      fixed-size backends  (PostScript,  XFig),  the
                      margins  settings  can  be used to control the
                      placement of the image on the  page.  If  only
                      one of the left and right margin is given, the
                      image will be placed this  distance  from  the
                      respective edge of the page, and similarly for
                      top and bottom. If margins are given on  oppo‐
                      site sides, the image is scaled to fit between
                      these margins,  but  not  if  the  scaling  is
                      already  determined  explicitly by one or more
                      of the -W, -H, -r, or -x options.

       -L dim, --leftmargin dim
                      set the left margin. See -M for details.

       -R dim, --rightmargin dim
                      set the right margin. See -M for details.

       -T dim, --topmargin dim
                      set the top margin. See -M for details.

       -B dim, --bottommargin dim
                      set the bottom margin. See -M for details.

   Output options:
       These options are only supported by certain backends.

       -C #rrggbb, --color #rrggbb
                      set the foreground color of the output  image.
                      The  default  is  black. This option works for
                      the PS/EPS, SVG, and XFig backends.

       --fillcolor #rrggbb
                      set the fill color of the output image,  i.e.,
                      the color of the "white" parts. The default is
                      to leave these parts transparent. This  option
                      works  for the PS/EPS, SVG, and XFig backends.
                      Implies --opaque.

       --opaque       fill in the white parts of the image opaquely,
                      instead of leaving them transparent. This only
                      applies to interior white parts,  i.e.,  those
                      which  are  enclosed  inside  a black outline.
                      This option works for the PS/EPS and SVG back‐
                      ends.  Opaqueness  is always in effect for the
                      XFig backend.

       --group        try to group related paths together in the SVG
                      output. Each path is grouped together with all
                      paths that are contained inside  it,  so  that
                      they can be moved around as a unit with an SVG
                      editor. This makes coloring individual  compo‐
                      nents slightly more cumbersome, and thus it is
                      not the default.

   PostScript/EPS options:
       -P format, --pagesize format
                      set page size. This is primarily used for  the
                      PostScript  backend.  In case of the EPS back‐
                      end, it may influence the default image  size.
                      The  following  formats  can be specified: a4,
                      a3, a5, b5, letter, legal, tabloid, statement,
                      executive,  folio,  quarto,  10x14.  Also,  an
                      argument of the form dimxdim  is  accepted  to
                      specify arbitrary dimensions. The default page
                      size is letter (or a4, if this was  configured
                      at  compile  time, see COMPILE TIME CONFIGURA‐
                      TION below).  Page format names can be  abbre‐
                      viated by an unambigous prefix.

       -c, --cleartext
                      do  not  compress the output. This option dis‐
                      ables the use of compression  filters  in  the
                      PostScript  output.  If  the -q option is also
                      used, the resulting output can be easily  read
                      by other programs or even by humans.

       -2, --level2   use  PostScript level 2 compression (default).
                      The resulting file size  is  ca.  40%  smaller
                      than if the -c option is used.

       -3, --level3   use  PostScript level 3 compression, if avail‐
                      able. This gives slightly smaller  files  than
                      using  -2,  but  the  resulting  files may not
                      print on older PostScript level 2 printers. If
                      support for PostScript level 3 compression has
                      been disabled at compile time, a warning  mes‐
                      sage  is  printed  and  level 2 compression is
                      used instead.

       -q, --longcoding
                      turn off optimized numerical coding. Normally,
                      potrace  uses  a very compact numerical format
                      to represent Bezier curves in PostScript, tak‐
                      ing  advantage of some redundancy in the curve
                      parameters. This option disables  this  behav‐
                      ior,  resulting  in  longer, but more readable
                      output (particularly if the -c option is  also

   PGM options:
       -G n, --gamma n
                      set the gamma value for anti-aliasing (default
                      is 2.2). Most computer displays do not  render
                      shades of grey linearly, i.e., a grey value of
                      0.5 is not displayed as being exactly half-way
                      between  black  and white. The gamma parameter
                      corrects for  this,  and  therefore  leads  to
                      nicer looking output. The default value of 2.2
                      is appropriate for most normal CRT displays.

   Frontend options:
       -k n, --blacklevel n
                      set the threshold level for  converting  input
                      images   to  bitmaps.  The  potrace  algorithm
                      expects a bitmap, thus all pixels of the input
                      images  are converted to black or white before
                      processing begins.  Pixels whose brightness is
                      less  than n are converted to black, all other
                      pixels to white. Here n is a number between  0
                      and  1.  One case is treated specially: if the
                      input is  in  an  indexed  color  format  with
                      exactly  2  colors,  then  the  blacklevel  is
                      ignored and the darker of the  two  colors  is
                      mapped to black.

                      Note:  the method used by potrace for convert‐
                      ing greymaps to bitmaps is  very  crude;  much
                      better  results  can be obtained if a separate
                      program, such as mkbitmap(1), is used for this
                      purpose.  In particular, mkbitmap(1), which is
                      distributed with potrace, has the  ability  to
                      scale and interpolate the image before thresh‐
                      olding, which results in much better preserva‐
                      tion of detail.

       -i, --invert   invert the input bitmap before processing.

       Certain  aspects of the behavior of potrace can be configured
       at compile time by  passing  the  following  options  to  the
       ./configure script.

       --disable-zlib compile  potrace  without the zlib compression
                      library. This means PostScript  level  3  com‐
                      pression will not be available.

                      compile   potrace   with  centimeters  as  the
                      default unit instead of inches.

       --enable-a4    compile potrace with A4 as  the  default  page

       The  exit status is 0 on successful completion, 1 if the com‐
       mand line was invalid, and 2 on any other error.


       Peter Selinger <selinger at>

       For a detailed technical description  of  the  potrace  algo‐
       rithm,  see the file potrace.pdf, which is available from the
       potrace web site.

       The   latest   version   of   potrace   is   available   from  This  site  also contains a
       list of frequently asked questions, as well as information on
       how to obtain support.


       Copyright (C) 2001-2005 Peter Selinger

       This program is free software; you can redistribute it and/or
       modify it under the terms of the GNU General  Public  License
       as  published by the Free Software Foundation; either version
       2 of the License, or (at your option) any later version.

       This program is distributed in the hope that it will be  use‐
       ful,  but WITHOUT ANY WARRANTY; without even the implied war‐
       See the GNU General Public License for more details.

       You  should  have  received  a copy of the GNU General Public
       License along with this program; if not, write  to  the  Free
       Software  Foundation,  Inc., 59 Temple Place, Suite 330, Bos‐
       ton, MA 02111-1307, USA. See also

Version 1.7                  March 2005                   potrace(1)
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