Enhancing Readability with a Target-Aware Zooming Technique for Touch Surfaces

Double-tapping is a common way to zoom in and out of content on touch surfaces, snapping between overview and detail levels. However, the optimal zoom level often differs for each user depending on the displayed content and user characteristics (e.g., age or visual acuity). When focusing on content containing text, the scaling factor is especially crucial for readability. However, the conventional double-tap to zoom uses a fixed scale factor, which often requires users to manually adjust the zoom level by pinching in and out after double-tapping. Additionally, on small-screen devices such as smartphones, the specific area of interest may not fit within the screen after zooming in, causing users to pan repeatedly to adjust the display position of the content. To address these issues, we propose a target-aware zooming technique that dynamically adjusts the zoom level based on the content and user preferences. Furthermore, to minimize the need for panning, our technique simultaneously snaps the top-left corner of the bounding box of the tapped text to the top-left corner of the screen as the content is zoomed in. This approach aims to reduce the need for manual adjustments, improving usability and readability of digital content for diverse user groups.