In this paper, we present a drawing workstation for blind people using a two-dimensional tactile pin-matrix display for in- and output. Four different input modalities, namely menu-based, gesture-based, freehand-stylus and a Time-of-Flight (ToF) depth segmentation of real-world object silhouettes, are utilized to create graphical shapes. Users can freely manipulate shapes after creation. Twelve blind users evaluated and compared the four image creation modalities. During evaluation, participants had to copy four different images. The results show that all modalities are highly appropriate for non-visual drawing tasks. There is no generally preferred drawing modality, but most participants rated the robust and well-known menu-based interaction as very good. Furthermore, menu was second in performance and the most accurate drawing modality. Our evaluation demonstrated direct manipulation works well for blind users at the position of the reading hand. In general, our drawing tool allows blind users to create appealing images.

The Tangram Workstation is a collaborative system for creating tactile graphics. A transcriber composing a tactile graphic from a visual source is supported by a non-visual reviewer on a two-dimensional tactile pin-matrix device on which he can observe and adapt the work of his sighted team member. We present the results of an evaluation with eight teams, each consisting of a transcriber and a blind reviewer. Overall, quality of tactile graphics can be improved by a collaborative approach. In most cases blind users recommended changes on tactile graphics even when they have been prepared by professional sighted editors. The study also showed that the blind reviewer is able to do simple editing tasks independently with our workstation.