randallknutson / react-signature-canvas

A signature pad implementation for React. Unopinionated fork of react-signature-pad

React Signature Canvas

A signature pad implementation in React.

This is an unopinionated fork of react-signature-pad that does not impose any styling or wrap any other unwanted elements around your canvas -- it's just a wrapper around a single canvas element! Hence the naming difference.

This fork also allows you to directly pass props to the underlying canvas element, has small API differences, and documents the props you can pass to it.

Installation

npm i -S react-signature-canvas

Usage

import React from 'react'
import ReactDOM from 'react-dom'
import SignatureCanvas from 'react-signature-canvas'

ReactDOM.render(
  <SignatureCanvas penColor='green'
    canvasProps={{width: 500, height: 200, className: 'sigCanvas'}} />,
  document.getElementById('react-container')
)

Props

The props of SignatureCanvas mainly control the properties of the pen stroke used in drawing. All props are optional.

• velocityFilterWeight : number, default: 0.7
• minWidth : number, default: 0.5
• maxWidth : number, default: 2.5
• dotSize : number or function, default: () => (this.props.minWidth + this.props.maxWidth) / 2
• penColor : string, default: 'black'

There are also two callbacks that will be called when a stroke ends and one begins, respectively.

• onEnd : function
• onBegin : function

Two additional props are used to control the canvas element. canvasProps are directly passed to the underlying <canvas /> element and backgroundColor is used in the API's clear convenience method (which itself is called internally during resizes)

• canvasProps: object
• backgroundColor : string, default: 'rgba(0,0,0,0)'

API

All API methods require a ref to the SignatureCanvas in order to use and are instance methods of the ref.

<SignatureCanvas ref={(ref) => { this.sigCanvas = ref }} />

• isEmpty() : boolean, self-explanatory
• clear() : void, clears the canvas using the backgroundColor prop
• fromDataURL(base64String) : void, writes a base64 image to canvas
• getCanvas(): canvas, returns the underlying canvas ref. Allows you to modify the canvas however you want or call methods such as toDataURL()
• getTrimmedCanvas(): canvas, creates a copy of the canvas and returns a trimmed version of it, with all whitespace removed.

Example

$ npm start

Navigate to http://localhost:8080/ in your browser and you should be able to see the signature canvas in action.

The source code for this example is found in the example/ directory.