Ubuntu Manpage: potrace - transform bitmaps into vector graphics.

NAME

       potrace - transform bitmaps into vector graphics.

SYNOPSIS

       potrace [options] [filename...]

DESCRIPTION

       potrace is a tool 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 output is SVG, PDF, EPS, or one of a number of other vector formats.  A  typical  use  is  to  create
       vector  graphics  from  scanned  data,  such  as company or university logos, handwritten notes, etc. The
       resulting image is not "jaggy" like a bitmap, but smooth. It can then be rendered 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 values 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: SVG, PDF, EPS, PostScript, DXF, GeoJSON, PGM,
       Gimppath, and XFig.  Additional backends might be added in the future.

OPTIONS

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 configured at compile time,
see COMPILE TIME CONFIGURATION below). For pixel-based output formats such as PGM, DXF, GeoJSON, and
Gimppath, the default unit is pixels.

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

-v, --version print version info and exit. This also shows the defaults that were compiled into this
version of potrace.

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

Input/output options:
filename Each file can hold an input image, or multiple concatenated input images. 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 filename 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 output
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
standard 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 only allowed for multi-page backends (see BACKEND
TYPES below). In this case, each input file may contain one or more bitmaps, and all the
bitmaps from all the input files are processed and the output concatenated into a single
file. A filename of "-" may be given to specify writing to standard output.

-- End of options. Any remaining arguments are interpreted as filenames. This also disables
filter mode, even if no filenames are given. This is useful for shell scripts, because
potrace -- $FILENAMES will behave correctly even for an empty list of filenames. However,
-- with an empty list of filenames is not permitted in conjunction with the -o option,
because this would generate a document of zero pages, which none of the backends permit.

Backend selection:
For general information, see also BACKEND TYPES below.

-b name, --backend name
Select backend by name, where name is one of eps, postscript, ps, pdf, pdfpage, svg, dxf,
geojson, pgm, gimppath, xfig. Backend names can be abbreviated by a prefix as long as it
is unambiguous. Backend names are case insensitive.

-s, --svg, -b svg, --backend svg
SVG backend. The output is a Scalable Vector Graphics (SVG) file. This is a single-page,
variable-sized, dimension-based backend. Note that unless the -r option is given, the
resolution of the input bitmap is assumed to be 72dpi.

-b pdf, --backend pdf
PDF backend. The output is a file in the Portable Document Format. If the input consists
of multiple bitmaps, they are each rendered on a separate page. This is a multi-page,
variable-sized, dimension-based backend.

-b pdfpage, --backend pdfpage
The PDFPage backend is like the PDF backend, except that it is fixed-size like the
PostScript backend.

-e, --eps, -b eps, --backend eps
EPS backend (default). The output is an encapsulated PostScript file. This is a single-
page, variable-sized, dimension-based backend.

-p, --postscript, -b ps, --backend ps
PostScript backend. The output is a PostScript file. This is a multi-page, fixed-size,
dimension-based backend. If the input consists of multiple bitmaps, they are each rendered
on a separate page.

-b dxf, --backend dxf
DXF backend. The output is a file in the Drawing Interchange Format (DXF). In this
backend, all Bezier curves are approximated by piecewise circular arcs; this is suitable
for processing in CAD software or for machining applications using CNC tools. This is a
single-page, variable-sized, pixel-based backend. The -u option has no effect for this
backend.

-b geojson, --backend geojson
GeoJSON backend. The output is a file in the format used by some applications processing
geographical data. In this backend, all Bezier curves are approximated by 8 straight line
segments. This is a single-page, variable-sized, pixel-based backend. The -u option has no
effect for this backend.

-g, --pgm, -b pgm, --backend pgm
PGM backend. The output is a portable greymap (PGM) file. It is a convenient backend for
antialiasing a bitmap image. This is a multi-page, variable-sized, pixel-based backend. If
the input consists of more than one image, the images are concatenated in the output.

-b gimppath, --backend gimppath
Gimppath backend. This backend produces output suitable to be imported as a path by the
GNU Image Manipulation Program (Gimp) (in the Layers, Channels & Paths dialog, select
Paths, then right-click and select Import Path). The output is actually an SVG file. The
differences to the SVG backend are: the --opaque option has no effect, the --flat option
is always on, and the dimensions are pixel-based. This is a single-page, variable-sized,
pixel-based backend.

-b xfig, --backend xfig
XFig backend. This is a single-page, fixed-size, dimension-based backend. The output is a
file in the XFig format. Note that XFig uses X-splines instead of Bezier curves, thus it
is not possible 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 segment. The -u option has no effect for this backend, because control points
are always rounded to the nearest 1/1200 of an inch in XFig. Curve optimization is
disabled. Implies --opaque.

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 unambiguous 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 0, then no smoothing will be
performed and the output is a polygon. If this parameter is greater than 4/3, then all
corners are suppressed and the output is completely smooth.

-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
size.

-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. This option has no effect for the XFig backend, which always
rasterizes to 1/1200 inch, or for the DXF backend. For the GeoJSON backend, this option is
only a hint; the actual rounding may be more, but not less, accurate than specified.

-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:
-P format, --pagesize format
for fixed-size backends, set page size. The following formats can be specified: A4, A3,
A5, B5, Letter, Legal, Tabloid, Statement, Executive, Folio, Quarto, 10x14. Format names
are case insensitive. 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 CONFIGURATION below). Page format names can be abbreviated
by a prefix as long as it is unambiguous. This option has no effect for variable-sized
backends.

-W dim, --width dim
set the width of output image (before any rotation and margins). 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 details.

-r n[xn], --resolution n[xn]
for dimension-based backends, set the resolution (in dpi). One inch in the output image
corresponds to this many pixels in the input. Note that a larger value results in a
smaller output image. It is possible to specify separate resolutions in the x and y
directions by giving an argument of the form nxn. For variable-sized backends, the default
resolution is 72dpi. For fixed-size backends, there is no default resolution; the image is
by default scaled to fit on the page. This option has no effect for pixel-based backends.
If -W or -H are specified, they take precedence.

-x n[xn], --scale n[xn]
for pixel-based backends, set the scaling factor. A value greater than 1 enlarges the
output, a value between 0 and 1 makes the output smaller. The default is 1. It is possible
to specify separate scaling factors for the x and y directions by giving an argument of
the form nxn. This option has no effect for dimension-based backends. If -W or -H are
specified, they take precedence.

-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 compressed in the y direction.

-A angle, --rotate angle
set the rotation angle (in degrees). The output 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 and default value of this option depend on the backend.
For variable-sized backends, the margins will simply be added around the output image (or
subtracted, in case of negative margins). The default margin for these backends is 0. For
fixed-size backends, the margin 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 opposite sides, the image is scaled to fit between these margins,
unless the scaling is already determined explicitly by one or more of the -W, -H, -r, or
-x options. By default, fixed-size backends use a non-zero margin whose width depends on
the page size.

-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.

--tight remove whitespace around the image before scaling and margins are applied. If this option
is given, calculations of the width, height, and margins are based on the actual vector
outline, rather than on the outer dimensions of the input pixmap, which is the default. In
particular, the --tight option can be used to remove any existing margins from the input
image. See the file placement.pdf for a more detailed illustration.

Color options:
These options are only supported by certain backends. The DXF and GeoJSON backends do not support color.

-C #rrggbb, --color #rrggbb
set the foreground color of the output image. The default is black.

--fillcolor #rrggbb
set the fill color of the output image, i.e., the color of the "white" parts that are
enclosed by "black" parts. The default is to leave these parts transparent. Implies
--opaque. Please note that this option sets the background color; to set the foreground
color, use --color instead.

--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 that are enclosed inside a black
outline. Opaqueness is always in effect for the XFig backend.

SVG options:
--group for SVG output, try to group related paths together. 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 components slightly more cumbersome, and thus
it is not the default.

--flat for SVG output, put the entire image into a single path. This makes it impossible to color
the components individually, and thus it is not the default. But the resulting SVG file
can be more easily imported by some applications such as Gimp. In fact, the Gimppath
backend is a variation of the SVG backend with the --flat option and pixel-based scaling.
The --flat option has no effect if --opaque has been selected.

PostScript/EPS/PDF options:
-c, --cleartext
do not compress the output. This option disables the use of compression filters in the
PostScript and PDF output. In the PostScript backend, if -c and -q are used together, 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 available. 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
message is printed and level 2 compression is used instead.

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

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 converting 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 thresholding, which results in much
better preservation of detail.

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

Progress bar options:
--progress display a progress bar for each bitmap that is processed. This is useful for interactive
use. The default behavior is not to show any progress information.

--tty mode set the terminal mode for progress bar rendering. Possible values are "vt100", which
requires a vt100-compatible terminal, and "dumb", which uses only ASCII characters. The
default is system dependent.

BACKEND TYPES

Backends can be classified in several ways, which affects the available command line options and their
behavior:

Fixed-size or variable-sized:
For fixed-size backends, the size of the page is always the same (for example Letter or A4, as
specified at compile time or by the -P option). By default, the image will be centered and scaled to
fit the page size. For variable-size backends, the size of the page follows the size of the image.
Currently the PostScript (PS), PDFPage, and XFig backends are fixed-size, and the remaining backends
are variable-size.

Dimension-based or pixel-based:
In dimension-based backends, distances are measured in physical units such as inches or centimeters.
In pixel-based backends, distances are measured in pixel units. The -r option only works for
dimension-based backends, and the -x option only works for pixel-based backends. Currently, the DXF,
PGM, Gimppath, and GeoJSON backends are pixel-based, and the remaining backends are dimension-based.
Currently, all pixel-based backends are variable-sized.

Single-page or multi-page:
Single-page backends can only accept a single image. Multi-page backends can accept multiple images,
typically one per page of output. Currently, the PostScript (PS), PDF, PDFPage, and PGM backends are
multi-page, and the remaining backends are single-page. Note that multiple input images can be read
in two ways: from multiple input files (with the -o option), or from a single input file that holds
several concatenated images.

COMPILE TIME CONFIGURATION

       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 compression will
            not be available.

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

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

EXIT STATUS

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

VERSION

       1.16

AUTHOR

       Peter Selinger <selinger at users.sourceforge.net>

       Please see the file AUTHORS for a full list of other contributors.

TECHNICAL DOCUMENTATION

       For  a  detailed  technical  description  of  the  potrace  algorithm, see the file potrace.pdf, which is
       available from the potrace web site. For information on the Potrace library API, see potracelib.pdf.

WEB SITE AND SUPPORT

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

COPYRIGHT

       Copyright (C) 2001-2019 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 useful, but WITHOUT ANY WARRANTY; without even
       the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.   See
       also http://www.gnu.org/.

Version 1.16                                     September 2019                                       potrace(1)