Gliding a finger on touchscreen to reach a target, that is, touch exploration, is a common selection method of blind screen-reader users. This paper investigates their gliding behavior and presents a model for their motor performance. We discovered that the gliding trajectories of blind people are a mixture of two strategies: 1) ballistic movements with iterative corrections relying on non-visual feedback, and 2) multiple sub-movements separated by stops, and concatenated until the target is reached. Based on this finding, we propose the mixture pointing model, a model that relates movement time to distance and width of the target. The model outperforms extant models, improving R 2 from 0.65 for Fitts' law to 0.76, and is superior in cross-validation and information criteria. The model advances understanding of gliding-based target selection and serves as a tool for designing interface layouts for screen-reader based touch exploration.
CCS CONCEPTS• Human-centered computing → Pointing; Accessibility theory, concepts and paradigms.
People with low vision who use screen magnifiers to interact with computing devices find it very challenging to interact with dynamically changing digital content such as videos, since they do not have the luxury of time to manually move, i.e., pan the magnifier lens to different regions of interest (ROIs) or zoom into these ROIs before the content changes across frames.In this paper, we present SViM, a first of its kind screen-magnifier interface for such users that leverages advances in computer vision, particularly video saliency models, to identify salient ROIs in videos. SViM's interface allows users to zoom in/out of any point of interest, switch between ROIs via mouse clicks and provides assistive panning with the added flexibility that lets the user explore other regions of the video besides the ROIs identified by SViM.Subjective and objective evaluation of a user study with 13 low vision screen magnifier users revealed that overall the participants had a better user experience with SViM over extant screen magnifiers, indicative of the former's promise and potential for making videos accessible to low vision screen magnifier users.
CCS CONCEPTS• Human-centered computing → Human computer interaction (HCI); Accessibility systems and tools; User studies.
Consuming video content poses significant challenges for many screen magnifier users, which is the "go to" assistive technology for people with low vision. While screen magnifier software could be used to achieve a zoom factor that would make the content of the video visible to low-vision users, it is oftentimes a major challenge for these users to navigate through videos. Towards making videos more accessible for low-vision users, we have developed the SViM video magnifier system [6]. Specifically, SViM consists of three different magnifier interfaces with easy-touse means of interactions. All three interfaces are driven by visual saliency as a guided signal, which provides a quantification of interestingness at the pixel-level. Saliency information, which is provided as a heatmap is then processed to obtain distinct regions of interest. These regions of interests are tracked over time and displayed using an easy-to-use interface. We present a description of our overall design and interfaces. CCS CONCEPTS • Human-centered computing ~ Accessibility technologies KEYWORDS Screen magnifier users, video accessibility Figure 1: Top: Original image. Bottom: Heatmap and sample ROIs(Photo at the top is derived from video by Freestocks (CC BY 3.0)).
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