react-native-free-canvas

Freehand sketch on canvas based on @shopify/react-native-skia

Install

You need to install following dependencies

"@shopify/react-native-skia": ">=1.0.0",
"react": ">=18.0.0",
"react-native": ">=0.72.0",
"react-native-gesture-handler": ">=2.0.0",
"react-native-reanimated": ">=3.0.0"

Usage

import FreeCanvas from 'react-native-free-canvas';

const App = () => {
  return (
    <>
      <FreeCanvas
        // style={{flex: 1}} 
        style={styles.flex1} //avoid using a new Object to prevent unnecessary re-rendering
      />
    </>
  )
};

Make Line Smoother

import {CornerPathEffect} from '@shopify/react-native-skia';

const effects = useMemo(() => <CornerPathEffect r={32} />, []);

// Add CornerPathEffect component to pathEffect props
<FreeCanvas
  // style={{flex: 1}}
  style={styles.flex1}
  pathEffect={effects} 
/>

Properties

Property	Type	Description
style	StyleProp<ViewStyle>	Custom styles for the canvas
strokeColor	string | SharedValue<string>	Color of the stroke
strokeWidth	number | SharedValue<number>	Width of the stroke
backgroundColor	string | SharedValue<string>	Background color of the canvas
background	React.ReactNode	Skia component for background
foreground	React.ReactNode	Skia component for foreground
pathEffect	React.ReactNode	Skia Path Effects (see documentation)
zoomable	boolean	Enable/disable zooming
onDrawEnd	() => void	Callback function when drawing ends
onTranslate	(x: number, y: number) => void	Worklet function that runs on UI thread when canvas is translated
onScale	(scale: number) => void	Worklet function that runs on UI thread when canvas is scaled
onTransformOriginChange	(x: number, y: number) => void	Worklet function that runs on UI thread when transform origin changes

Transform & Scale

The order of the transform and scale in animated style for the Canvas while zooming should be:

{
  transform: [
    { translateX: translateSharedVal.value.x },
    { translateY: translateSharedVal.value.y },
    { scale: scaleSharedVal.value },
  ],
  transformOrigin: originSharedVal.value.concat([0]),
}

Methods or Values

Method	Parameters	Return Type	Description
reset	-	void	Resets the canvas
resetZoom	(duration?: number)	void	Resets the zoom level
undo	(step?: number)	void	Undoes the last drawing action(s)
toBase64	(fmt?: ImageFormat, quality?: number)	Promise<string | undefined>	Converts canvas to base64 string
getSnapshot	-	Promise<SkImage | undefined> | undefined	Gets a snapshot of the canvas
toPaths	-	DrawnPath[]	Returns the drawn paths
drawPaths	(paths: DrawnPath[])	void	Draws the given paths on the canvas
translateSharedValue	-	SharedValue<{ x: number; y: number }>	Shared value for translation
scaleSharedValue	-	SharedValue<number>	Shared value for scale
transformOriginSharedValue	-	SharedValue<[number, number]>	Shared value for transform origin

Inspired By

wobsoriano/rn-perfect-sketch-canvas A React Native component for drawing perfect pressure-sensitive freehand lines using perfect-freehand and Skia renderer.