Karbon

The second candidate we tested is licensed under the LGPL/GPL and is part of Calligra, the free KDE graphics and office suite. Karbon [2] is a vector drawing program. Like the other programs in the collection, it uses the open document format to the extent possible. The tested version 2.9.2 was released in April 2015.

Karbon combines shape templates with suitable drawing functions. Like Inkscape, the software arranges the tools in a toolbar on the left; the options are in a docking area on the right edge of the window. The KDE program also provides dockable dialogs that users can access from the Settings menu.

Shapes such as ellipses, stars, and rectangles can be found in the Add Shape palette. Two other buttons add external graphics and text to the drawing. The objects can be moved into the document by clicking or dragging and dropping. For scaling, the Shift key can be used to keep the aspect; pressing the Control key restricts the aspect ratios to integer values.

Users can change the radius of a rectangle using drag points or the text field in the Tool Options – asymmetrically, too, on request. A drag point defines the visible arc segment for ellipses. Alternatively, users can type the start and end angles manually in the dialog. Karbon can also create arcs, pie slices, and cross sections.

Other templates are hidden in the drop-down menu (Figure 3). Most of the templates can be formed using the mouse. Stars turn into polygons, and it is possible to configure the number of corners and edges.

Figure 3: Calligra Karbon contains all kinds of ready-made object templates that users can customize and use as templates for their own sketches.

Light and Shade

The Bezier curve tool works similarly to its counterpart in other programs. It is not, however, possible to add pointed nodes directly when drawing. This can only be done subsequently using the Path editing tool. The Freehand path tool, on the other hand, deserves a positive mention – it provides help in terms of accuracy and activates the smoothing algorithm when you select the Optimize checkbox.

A collection of features can be used to round off corners, swirl objects, and more in the Effects menu. Users can also define colored shadows in the object properties. You can show rulers, guides, and a grid and use the Snap to Grid function via the View menu; drawing objects now snap in when moving.

Karbon has virtually no documentation, which is unusual – most KDE manuals are quite extensive and translated into multiple languages. Without documentation, experimentation is the order of the day because some of the menus and dialogs are anything but intuitive, and functions are sometimes hidden.

This software was the only candidate in the test to suffer from stability problems: Simply selecting two nodes partially and repeatedly ensured that Karbon changed the shape of the curve independently. Clicked and activated drag points also sometimes lost focus during dragging.

LibreOffice Draw

The Draw [3] drawing program is already in place on many Linux computers as part of the LibreOffice package. At the beginning of the version 4 series, the developers licensed the project's source code under the GPLv3; the program itself is licensed under the LGPLv3 and the MPL 1.1. The test team checked out the current 4.4.2 version from April 2015.

It is clear to see here that Draw has never been patterned after pure graphics programs, but rather on drawing functions from other office packages. Even today, the focus is not really on drawing functions; instead the program impresses with ready-made shapes (Figure 4).

Figure 4: LibreOffice Draw's unique selling point: The program provides many pre-made shapes that users can drag from the palettes into the drawing.

The templates are special because of their flexibility: Some templates show a drag point highlighted in yellow after clicking, which then can be used to modify the object as desired. The numerous templates, which can be interactively shaped, save much time when visualizing flowcharts, network topologies, and mind maps. Those who think that manual drawing in Inkscape and sK1 is too much work should give Draw a chance.

The Extrusion function from the 3D symbol toolbar is surprisingly powerful. For example, it converts arcs into three-dimensional pie charts, including 3D highlighting, in just a few clicks. The feature is available for almost all shape templates. Converting Bezier curves is not possible, however.