Visual to Tactile Conversion of Vector Graphics

Methods to automatically convert graphics into raised-line images have been recently investigated. In this paper, concepts from previous research are extended to the vector graphics case, producing tactile pictures in which important features are emphasized. The proposed algorithm extracts object boundaries and employs a classification process, based on a graphic´s hierarchical structure, to determine critical outlines. A single parameter is introduced into the classification process, enabling users to tailor graphics to their own preferences. The resulting outlines are printed using a Braille printer to produce tactile output. Critical outlines are embossed with raised dots of highest height while other lines and details are embossed with a lower height. Psychophysical experiments including discrimination, identification, and comprehension are utilized to evaluate and compare the proposed algorithm. Results indicate that the proposed method outperforms other methods in all three considered tasks. The results also show that emphasizing important features significantly increases comprehension of tactile graphics, validating the proposed method´s effectiveness in conveying visual information.