PhotoEditor is an Android library (published on Maven Central) that provides a comprehensive image editing SDK. It allows users to draw on images with customizable brushes and shapes (line, oval, rectangle, arrow), apply filter effects via Android's deprecated MediaEffect API, add and edit text with rich styling (color, font, shadow, border), insert emoji and stickers, and perform pinch-to-scale/rotate gestures on added elements. The library is built around a `PhotoEditorView` custom RelativeLayout that composes an ImageView, a DrawingView (custom canvas for brush/shape rendering), and an ImageFilterView (GLSurfaceView for filters). The architecture employs several design patterns: Builder (PhotoEditor, ShapeBuilder, TextStyleBuilder, SaveSettings), Composite (Graphic interface with Text, Sticker, Emoji implementations), Strategy (Shape interface with concrete shapes), and Listener (OnPhotoEditorListener, BrushViewChangeListener). The sample app demonstrates all features. The library has a robust undo/redo system managed by GraphicManager and PhotoEditorViewState. While the core functionality is solid, the filter implementation relies on deprecated Android APIs (android.media.effect), which is a known limitation and source of issues. The codebase is well-structured with unit and instrumentation tests, CI/CD pipelines, and proper Kotlin coroutines for async saving.

The LLM identified 3 files worth highlighting for reuse: