Pencil is a free Firefox 3 extension used to create and edit diagrams and interface prototypes.
Pencil allows you to create illustrations as if they were drawn on paper. You can also create 2D animations using traditional drawing techniques, since Pencil includes a wide range of tools for you to use at will.
With this open source and multi-platform software, you can create background images for web sites and documents, install templates created by other users, generate graphics and vectors, and create all kinds of illustrations. You can either start from scratch, or make any change you may need and implement new elements in the existing templates and files.
On the one hand, Pencil includes a wide range of geometrical figures, comment templates, bullets and other elements for the design of web sites. On the other hand, it also provides tools to create hand-drawing like illustrations and to rotate, cut, transform, adjust, align, group and edit each of these elements, figures or drawings. As well as working with objects, Pencil allows you to work with enriched text and to apply any necessary final changes to your graphics and illustrations.
Also with this plug-in, you can animate a vectors illustration creating frame by frame animations, thanks to Pencil’s time and channels tool used to render the action. You can export the animation in video format (.mov) or flash (.swf). Besides, Pencil provides further export formats: raster graphics (PNG), text files (.odt y .doc), and PDF and HTML files.