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t.iv potrace
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u Interview with Peter Selinger
cotrace creator
http://potrace.sourceforge.net
Q - can you please introduce yourself
to our reader
My name is Peter Selinger. I am a
professor of mathematics at Dalhousie
University in Halifax, Canada. I
develop open-source software in my
free time.
Q - How did you get involved with
Commodore machines and do you still
actively use Commodore machines
My brother had a C-64 when I was 12 or
13 years old. I spent the next few
years programming it in Basic and
assembler. It was the first and only
Commodore machine I ever used.
Q - Can you tell our reader about
Potrace, what it does and how it
differs from similar applications?
Potrace is a utility for
raster-to-vector conversion. This
means, it inputs a bitmapped
black-and-white image, such as you
would get from a scanner or digital
camera, and turns it into a scalable
vector image using Bezier curves. The
output can be further processed with a
vector graphics editor such as
Inkscape.
There is other software with similar
functionality. Most of it is
commercial. In my opinion, none of it
gives output as nice looking as
Potrace's.
Q - What machines and operating
systems does the application run on
Potrace was written with portability
in mind, so it can run on virtually
any system that has a C compiler and
some POSIX-like library functions. It
was developed on Linux, and runs on
every flavour of Unix, Windows, and
the Macintosh. Alfred Faust ported it
to the Amiga (OS4) and Matthias
Rustler to AROS, the Amiga Research
Operating System (which runs on Intel
hardware)
Q - Any possibility of a GEOS or
Wheels version for Commodore 64 owners
The source code is available; with a C
compiler and some patience, I don't
see why someone could not compile it
for the Commodore 64. Of course, some
expanded RAM will be necessary, as the
Potrace source code runs to about 260
kilobytes, not including shared
libraries.
Q - I notice the software is Command
line only but other users have added
GUI versions, was your intention to
produce just a Command line version
Yes. Potrace adheres to the old Unix
philosophy of "doing only one thing,
and doing it well". This is why I call
it a "utility" and not an
"application". It has no fancy user
interface or add-on functionality. It
can be used in batch mode or scripts.
Potrace also can only read a handful
of image formats. There are other,
much better programs for converting
one image format to another.
Q - Can you tell our reader who
contributed to the project and what
they did
Potrace was almost entirely written by
myself. Tor Andersson wrote a backend
for outputting PDF. Karol Krenski
contributed the logo, which he of
course created using Potrace. Many
people have helped with finding and
reporting bugs.
Q - Our reader may.not be aware of the
"GNU General Public License". Can you
explain this does it mean the software
is free to use.
For a full explanation of the license,
read the file COPYING that is
distributed with Potrace. The short
answer is: yes, under the GNU General
Public License (GPL), you are free to
use the software.
However, much more is true: you are
also free to modify, recompile, and
redistribute it. The primary
restriction is that when you
redistribute (modified or unmodified)
versions of Potrace, you must again do
so under the terms of the GPL. This
means that nobody can integrate
Potrace, or anything derived from it,
into a non-GPL program without my
permission.
Please note that "free" in this
context refers to freedom, not to
price. There is lots of software that
is offered without payment, but that
does not give you any freedom. GPL
software is not like that.
Q - What other software have you
written, and are you working on any
other projects at the moment I have
written lots of software. The most
popular items besides Potrace are:
-Ccrypt, a simple and secure
command-line encryption program
(ccrypt.sourceforge.net)
-Upprint, a printer frontend for n-up
and double sided printing. N-up
printing means putting multiple pages
on a single sheet of paper at reduced
size. Most off-the-shelf software does
this very badly, by leaving huge
margins and making the text way too
small.
Q - I like the Potrace mascot can you
tell our reader a little about it.
The mascot was designed by Karol
Krenski, a Polish artist who was an
early and enthusiastic user of
Potrace. You can see some more of his
works at
www.sgsp.edu.pl/inne/galerie/krenski/k
renski.php
Q - what problems did you have
creating the software, was all the
code created by yourself or did you
manage to find something similar and
adapt it to your needs
The largest challenge in writing this
software was designing the Potrace
tracing algorithm. This is really the
heart of the software. I wrote all of
it myself, except for the PDF backend.
Q - I see this is a FAQ already but
for our reader who desnt read the
FAQ_s -Can Potrace scan and convert
Colour files as well as mono images,
are there plans for the software to
convert colour images
No, it cannot convert colour images.
Perhaps I will add this ability in the
future, but I do not currently have a
concrete plan to do so. There is some
software, such as Inkscape
(www.inkscape.org), which is able to
use Potrace on color images,
essentially by decomposing the image
into a series of bitonal images,
tracing each of them separately, and
then putting the results together
again.
Q - Does the software work equally
well on text or complex images
The best results are obtained on
handwriting and hand-drawn images such
as cartoons. Potrace also works
reasonably well on text, provided that
the characters have been rendered at a
high enough resolution. Complex images
are no problem, because Potrace is
quite fast even on most large images.
One thing that Potrace does not work
too well on is noisy images. It is
important to prepare the input image
carefully to get best tracing results.
I wrote another program called
"mkbitmap" that can help doing this.
It is distributed together with
Potrace.
Q - What is the current version of the
software and are there further
development charges planned
The current version is 1.8. Potrace is
quite stable at the moment, which
means it works reliably and there is
no need to make lots of changes to
the software.
Q - How can our reader help with the
project
Use Potrace and tell others about it!
Q - is there a forum for people with
problems using the software, can users
email you directly
For problems, users should first check
the Frequently Asked Questions
http://potrace.sourceforge.net/faq.htm
l
and then use the Forum and
http://sourceforge.net/projects/potrac
e
Q - what are the main problems
converting the software to other
platforms, can you give a quick how to
on conversion to our reader, is there
any help on converting lets say an
Amiga application to linux or even the
PC,
My main advice is to write the
software portably in the first place.
Fortunately for me, within the Unix
community, there are some
well-established standards for the
programming environment that any Unix
system should provide. One such set of
standards is known as POSIX. Since
POSIX environments are also available
for Windows and the Macintosh, porting
to those platforms was for the most
part not very difficult.
Q - I presume that command line
versions are quick to convert to other
platforms is this why you only
personally produced the command line
version of Potrace
No, portability was not a
consideration in my decision to
produce a command-line tool. Actually,
I use the command line a lot. If I
need to convert 200 images, I would
much rather write something like
"potrace *.pnm" than going through
some graphical user interface where I
have to manually click, drag, and drop
200 files. Tracing of images is not
fundamentally an interactive process.
Pretty much there is an input and an
output, and a few parameters that one
can tweak along the way. So I never
saw the need for a graphical
interface. However, others have
written such interfaces for Potrace.
See
http://potrace.sourceforge.net/#other
...end...