The importance of data charts is self-evident, given their ability to express complex data in a simple format that facilitates quick and easy comparisons, analysis, and consumption. However, the inherent visual nature of the charts creates barriers for people with visual impairments to reap the associated benefits to the same extent as their sighted peers. While extant research has predominantly focused on understanding and addressing these barriers for blind screen reader users, the needs of low-vision screen magnifier users have been largely overlooked. In an interview study, almost all low-vision participants stated that it was challenging to interact with data charts on small screen devices such as smartphones and tablets, even though they could technically "see" the chart content. They ascribed these challenges mainly to the magnification-induced loss of visual context that connected data points with each other and also with chart annotations, e.g., axis values. In this paper, we present a method that addresses this problem by automatically transforming charts that are typically non-interactive images into personalizable interactive charts which allow selective viewing of desired data points and preserve visual context as much as possible under screen enlargement. We evaluated our method in a usability study with 26 low-vision participants, who all performed a set of representative chart-related tasks under different study conditions. In the study, we observed that our method significantly improved the usability of charts over both the status quo screen magnifier and a state-of-the-art space compaction-based solution.

Data chart visualizations and text are often paired in news articles, online blogs, and academic publications to present complex data. While chart visualizations offer graphical summaries of the data, the accompanying text provides essential context and explanation. Associating information from text and charts is straightforward for sighted users but presents significant challenges for individuals with low vision, especially on small-screen devices such as smartphones. The visual nature of charts coupled with the layout of the text inherently makes it difficult for low vision users to mentally associate chart data with text and comprehend the content due to their dependence on screen magnifier assistive technology, which only displays a small portion of the screen at any instant due to content enlargement. To address this problem, in this paper, we present a smartphone-based multimodal mixed-initiative interface that transforms static data charts and the accompanying text into an interactive slide show featuring frames containing “magnified views” of relevant data point combinations. The interface also includes a narration component that delivers tailored information for each “magnified view”. The design of our interface was informed by a user study with 10 low-vision participants, aimed at uncovering low vision interaction challenges and user-interface requirements with multimodal documents that integrate text and chart visualizations. Our interface was also evaluated in a subsequent study with 12 low-vision participants, where we observed significant improvements in chart usability compared to both status-quo screen magnifiers and a state-of-the-art solution.