Easy Watermark is an open-source application for Android developed in Kotlin by rosu, designed to simplify the watermarking process for images. It features a user-friendly interface that allows users to add text and emoji watermarks with ease. The app provides various editing options, including fonts, sizes, colors, and angles, as well as a single tile mode to prevent watermark duplication. Users can also add custom logos using the 'Icon' option. Easy Watermark can be installed from F-Droid or purchased on the Play Store, and its source code is available on GitHub.