In a world driven by data visualization, ensuring the inclusive accessibility of charts for Blind and Visually Impaired (BVI) individuals remains a significant challenge. Charts are usually presented as raster graphics without textual and visual metadata needed for an equivalent exploration experience for BVI people. Additionally, converting these charts into accessible formats requires considerable effort from sighted individuals. Digitizing charts with metadata extraction is just one aspect of the issue; transforming it into accessible modalities, such as tactile graphics, presents another difficulty. To address these disparities, we propose Chart4Blind, an intelligent user interface that converts bitmap image representations of line charts into universally accessible formats. Chart4Blind achieves this transformation by generating Scalable Vector Graphics (SVG), Comma-Separated Values (CSV), and alternative text exports, all comply with established accessibility standards. Through interviews and a formal user study, we demonstrate that even inexperienced sighted users can make charts accessible in an average of 4 minutes using Chart4Blind, achieving a System Usability Scale rating of 90%. In comparison to existing approaches, Chart4Blind provides a comprehensive solution, generating end-to-end accessible SVGs suitable for assistive technologies such as embossed prints (papers and laser cut), 2D tactile displays, and screen readers. For additional information, including open-source codes and demos, please visit our project page https://moured.github.io/chart4blind/.

Accessible alternatives to two-dimensional (2d) information are important in connecting people with blindness and visual impairment (BVI) to the rest of the world. Such 2d information for people with BVI includes, for example, line charts. Within line charts, it is a challenging task for people with BVI to distinguish lines. This is specifically difficult for charts with complex layouts that contain multiple lines, especially parallel lines and intersections. Tactile 2d graphic readers such as the Tactonom Reader allow access to line graph data via audio-tactile user interfaces (UIs), but these are not yet mature. Its current user interface (Tactonom Reader Version 1) combines tactile graphics (paper with Braille embossing or swell paper) with pinpointed audio explanations through camera-based fingertip recognition. Following a user-centred design, we implemented a new augmented user interface to distinguish lines of line charts in the Tactonom Reader. In addition to spoken explanations, the enhanced user interface uses acoustic feedback, supports dynamic trigger sounds and includes a component for filtering individual lines. Thus, we first evaluated the current speech user interface of the Tactonom Reader and our extended user interface for distinguishing lines of line diagrams with four participants with BVI. Beyond comparing the efficiency, effectiveness and satisfaction of both user interfaces with graphs of different complexity, we observed the current challenges of this task. The analysis revealed that the evaluated user interfaces enable people with BVI to access and distinguish lines in uncomplicated mathematical charts. Our new user interface has proved very useful in several areas but needs further development to fully enable people with BVI to understand and distinguish lines in complex mathematical diagrams.