Konva Canvas Library

Konva is an open-source 2D canvas library for JavaScript that enables high-performance desktop and mobile applications with shape manipulation, event handling, and layer management. Created by Anton Lavrenov, the library provides an object-oriented API for creating and manipulating shapes including rectangles, circles, ellipses, lines, polygons, stars, text, images, paths, and sprites on HTML5 Canvas elements. Konva organizes shapes into layers, with each layer rendered on its own canvas element, enabling selective redrawing of only changed layers for performance optimization when working with complex scenes containing hundreds or thousands of shapes. The event system handles mouse, touch, and pointer events through a stage-to-shape hit detection algorithm, supporting click, dblclick, mouseover, mouseout, drag, dragmove, transform, and wheel events with proper event delegation. The drag-and-drop system includes boundary constraints, drag bounds functions, and shadow effects during dragging. The transformation support includes scaling, rotation, and skewing through anchor points, with the Transformer node providing visual handles for user-driven resizing and rotation. Konva supports filters for color manipulation, blur, brighten, contrast, invert, threshold, pixelate, and custom convolution kernels. The library includes animation through the Animation class for frame-by-frame updates and Tween for smooth property transitions. Framework adapters exist for React through react-konva and Vue through vue-konva, enabling declarative shape composition within component trees.