konva

What is konva?

Konva is a 2D canvas library for JavaScript that enables developers to create complex and interactive graphics on the web. It is built on top of the HTML5 Canvas API and provides a high-level API for drawing shapes, images, text, and more. Konva is particularly useful for creating animations, interactive applications, and data visualizations.

What are konva's main functionalities?

Drawing Shapes

This feature allows you to draw various shapes such as circles, rectangles, and polygons. The code sample demonstrates how to create a stage, add a layer, and draw a red circle with a black border.

const stage = new Konva.Stage({ container: 'container', width: 500, height: 500 }); const layer = new Konva.Layer(); const circle = new Konva.Circle({ x: stage.width() / 2, y: stage.height() / 2, radius: 70, fill: 'red', stroke: 'black', strokeWidth: 4 }); layer.add(circle); stage.add(layer);

Handling Events

Konva provides an easy way to handle user interactions like clicks, mouse movements, and touch events. The code sample shows how to add a click event listener to a circle shape.

circle.on('click', function () { alert('Circle clicked!'); });

Animations

Konva supports animations, allowing you to create dynamic and interactive graphics. The code sample demonstrates how to animate a circle's position over time.

const anim = new Konva.Animation(function (frame) { circle.x(Math.sin(frame.time * 2 * Math.PI / 1000) * 100 + stage.width() / 2); }, layer); anim.start();

Transformations

You can apply transformations like scaling, rotation, and dragging to shapes. The code sample shows how to make a circle draggable and log a message during the drag event.

circle.draggable(true); circle.on('dragmove', function () { console.log('Circle is being dragged'); });

Text and Images

Konva allows you to add text and images to your canvas. The code sample demonstrates how to add a text element and an image to a layer.

const text = new Konva.Text({ x: 10, y: 10, text: 'Hello, Konva!', fontSize: 30, fontFamily: 'Calibri', fill: 'green' }); layer.add(text); const imageObj = new Image(); imageObj.onload = function () { const konvaImage = new Konva.Image({ x: 50, y: 50, image: imageObj, width: 100, height: 100 }); layer.add(konvaImage); layer.draw(); }; imageObj.src = 'path/to/image.jpg';

Other packages similar to konva

fabric

Fabric.js is a powerful and simple JavaScript HTML5 canvas library. It provides an interactive object model on top of the canvas element, making it easy to create and manipulate shapes, images, and text. Compared to Konva, Fabric.js offers more advanced features for object manipulation and is often used for applications like image editors and drawing tools.

paper

Paper.js is an open-source vector graphics scripting framework that runs on top of the HTML5 Canvas. It is designed to make it easy to work with vector graphics and bezier curves. Paper.js is more focused on vector graphics and offers a different set of tools compared to Konva, which is more general-purpose.

pixi.js

PixiJS is a fast 2D rendering engine that uses WebGL with a canvas fallback. It is designed for creating high-performance graphics and games. While Konva is more focused on ease of use and interactivity, PixiJS is optimized for performance and is often used in game development.

README

#Konva

Konva is an HTML5 Canvas JavaScript framework that enables high performance animations, transitions, node nesting, layering, filtering, caching, event handling for desktop and mobile applications, and much more.

You can draw things onto the stage, add event listeners to them, move them, scale them, and rotate them independently from other shapes to support high performance animations, even if your application uses thousands of shapes. Served hot with a side of awesomeness.

This repository began as a GitHub fork of ericdrowell/KineticJS.

• Visit: The Home Page and follow on Twitter
• Discover: Tutorials, API Documentation
• Help: StackOverflow

#Installation

• bower install konva
• npm install konva - for Browserify. For nodejs you have to install some dependencies
• CDN: https://rawgit.com/konvajs/konva/0.8.0/konva.min.js

###NodeJS

We are using node-canvas to create canvas element.

1. Install node-canvas https://github.com/LearnBoost/node-canvas/wiki/_pages
2. npm install jsdom
3. npm install konva

See file resources/nodejs-demo.js for example.

#Change log

See CHANGELOG.md.

#Dev environment

Before doing all dev stuff make sure you have node installed. After that, run npm install --dev in the main directory to install the node module dependencies.

Run grunt --help to see all build options.

##Building the Konva Framework

To build a development version of the framework, run grunt dev. To run a full build, which also produces the minified version and the individually minified modules for the custom build, run grunt full. You can also run grunt beta to generate a beta version.

If you add a file in the src directory, be sure to add the filename to the sourceFiles array variable in Gruntfile.js.

##Testing

Konva uses Mocha for testing.

• If you need run test only one time run grunt test.
• While developing it is easy to use grunt server with watch task. Just run it and go to http://localhost:8080/test/runner.html. After src file change konva-dev.js will be automatically created, so you just need refresh test the page.

Konva is covered with hundreds of tests and well over a thousand assertions. Konva uses TDD (test driven development) which means that every new feature or bug fix is accompanied with at least one new test.

##Generate documentation

Run grunt docs which will build the documentation files and place them in the docs folder.

#Pull Requests I'd be happy to review any pull requests that may better the Konva project, in particular if you have a bug fix, enhancement, or a new shape (see src/shapes for examples). Before doing so, please first make sure that all of the tests pass (grunt test).

Changelog

0.9.0 - 2015-02-27

Fixed

• cache algorithm has A LOT OF updates.

Changed

• scale now affects shadowOffset
• performance optimization (remove some unnecessary draws)
• more expected drawing when shape has opacity, stroke and shadow
• HDPI for caching.
• Cache should work much better. Now you don't need to pass bounding box {x,y,width,height} to cache method for all buildin Konva shapes. (only for your custom Konva.Shape instance).
• Tween now supports color properties (fill, stroke, shadowColor)

Added

• new methods for working with node's name: addName, removeName, hasName.
• new perfectDrawEnabled property for shape. See http://konvajs.org/docs/performance/Disable_Perfect_Draw.html
• new shadowForStrokeEnabled property for shape. See http://konvajs.org/docs/performance/All_Performance_Tips.html
• new getClientRect method.
• new to method for every node for shorter tweening