*2.2. Touchscreen Accessibility*

While we chose to focus on touchscreen-based image accessibility, touchscreen devices are innately inaccessible as they require accurate hand–eye coordination [26]. Thus, various studies have been conducted to improve touchscreen accessibility by providing tactile feedback using additional hardware devices [27–29]. *TouchCam*, for example, designed and implemented a camera-based wearable device that can be worn on a finger, which is used to access one's personal touchscreen devices by interacting with their skin surface to provide extra tactile and proprioceptive feedback. Physical overlays that can be placed on the top of a touchscreen were also investigated [6,30]. For instance, *TouchPlates* [6] allows people with visual impairments to interact with touchscreen devices by placing tactile overlays on the top of the touch display. Meanwhile, software-based approaches have been proposed as well such as supporting touchscreen gestures that can be performed anywhere on the screen [26,31–34]. *BrailleTouch* [32] and No-Look Notes [34], for example, proposed software solutions for supporting eyes-free text entry for blind users by using multi-touch gestures. Similarly, smartphones on the market also offer screen reader modules with location-insensitive gestures: iOS's VoiceOver (https://www.apple.com/accessibility/ vision/,accessedon15April2021) and Android's Talkback (https://support.google.com/ accessibility/android/answer/6283677?hl=en). These screen readers read out the contents on the screen if focused, and users can navigate different items by directional swipes (i.e., left-to-right and right-to-left swipe gestures) or by exploration-by-touch.

Again, we are interested in how touchscreen devices can be used to improve image accessibility mainly because they are readily available to a large number of end-users including BLV people as they have their own personal devices with touchscreens. In addition, as touchscreen devices offer screen reader functionality, they are accessible.
