Debian Package of the Day (static archived copy)

Article submitted by András Horváth. Guess what? We still need you to submit good articles about software you like!

You can face the task sometimes that you need a high resolution material from a particular image. Most probably when you’re a graphic designer (or even a tattoo artist), you might want to have a good quality result from a low resolution image that you can magnify no matter how much, it will give you smooth edges in high quality.

For this, you have the following possibility without a trace program: using a pixel graphic software like Gimp, you can resize the image with the best resampling method and apply a selective blur filter on it. Most of the times this doesn’t give the necessary quality.

There is a small but powerful utility called potrace developed by Peter Selinger, a mathematics professor at the Dalhousie University.

With a trace program like potrace, all you have to do is to give the image as an input, and there you have the result in the standard SVG format. potrace can produce even PDF format as an output.

Command-line example:

$ potrace -s image.bmp

With this process, the program transforms the images’ pixels into filled curves that have infinite resolution with smooth lines at any zoom.

In my personal experience while working as a graphic designer, potrace gave me very good results to many input images. Compared to other high expensive proprietary software, when the input image had sharp endings, potrace gave sharp edges in the result and other programs gave bad results, curving the edges. That needed a lot of manual correction.

Pros (compared to other programs):

• Very good results
• Pretty fast
• Can be easily run from a command-line
• Can be used from the Inkscape open-source vector graphics software (Path / Trace Bitmap menu or Shift+Alt+B)

Cons:

• Only 2 colors output (Black & White), no colored process is available yet
• potrace does not support PNG images as an input (though images can be converted easily from PNG with a whole variety of free programs)

This is an example found in the homepage, you can see the original bitmap and the vectorised image:

The package has been available both in Debian and Ubuntu since a long time ago.

Related links:

http://en.wikipedia.org/wiki/Potrace

http://wiki.inkscape.org/wiki/index.php/Potrace