PhotoView

PhotoView is an open-source library for Android that extends an ImageView to provide intuitive zooming and panning. It is widely used to display images users can zoom with gestures such as pinch and double-tap.

Key features include pinch-to-zoom, double-tap to zoom, smooth panning with drag, and configurable minimum and maximum zoom scales. The library uses matrix-based transformations and exposes listeners such as OnPhotoTapListener and OnViewTapListener to react to taps, enabling interactive image behavior within apps.

Usage involves adding the library as a dependency and replacing ImageView with PhotoView in layouts, or attaching a PhotoViewAttacher to an existing ImageView in code. It supports setting images from resources or drawables and works with standard Android image loading patterns.

Development and licensing: PhotoView was originally created by Chris Banes and is maintained as an open-source project by the community. It is released under the Apache License 2.0, allowing broad use in both open-source and proprietary applications.

The library is commonly used in image galleries, product viewers, and media apps to provide an out-of-the-box interactive image experience without implementing custom gesture handling.