Images can be grouped in two categories, pixel oriented and vector oriented. Pixel oriented data formats are jpg, gif, png and programs to edit and view them are numerous. A disadvantage is, when you zoom in, you will see the pixels and the picture is no more sharp.

A way to not have this effect is using lines (vectors) instead of pixels. A file format used in the GPL world is svg (Scalable Vector Graphics) and the program to edit such files is: inkscape

Unfortunately inkscape runs rather slow and has not a very intuitive user interface and needs therefore some training until it can be worked efficient. Some keyboard mouse operations are necessary to be known:

Drag mouse wheel > pan

Scroll mouse wheel > pans up and down

Shift scroll mouse wheel > pans left right

Click mouse wheel > zooms in

Shift click mouse wheel > zooms out

Inkscape is a program to draw vector graphics. The drawing is svg and this is an xml format that is directly supported by many programs as web browsers. Since it is xml, inkscape allows to go in xml mode where xml data can be observed and modified.

When the xml editor is opened also the drawing window stays open (maybe it get hidden by the full screen xml editor). Now in both windows can be worked and both windows are synchronized. This is a good way exploring svg and the drawing.

To have your personalized settings store an inkscape file under:

~/.inkscape/templates/default.svg

As File>New shows, inkscape can be used for many things as cd-covers, business cards, fontforge-glyph, Open A4 landscape and turning on the grid gives something ready for making a drawing on a 1mm grid (where it snaps when close) and 5mm major gridlines.

The secret of drawing straight lines is selecting Bezier curves (but pressing the Ctrl Button) when left clicking the mouse button to get a straight line between points. This can be continued until CR or mouse right click happens.