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baldr-react-native-sketch-canvas
npm i baldr-react-native-sketch-canvas
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baldr-react-native-sketch-canvas

react-native-sketch-canvas allows you to draw / sketch on both iOS and Android devices and sync the drawing data between users. Of course you can save as image.

by Terry Lin, Thomas Steinbrüchel, Baldr SAS

0.8.15 (see all)License:MITTypeScript:Not FoundCategories:React Native Canvas
npm i baldr-react-native-sketch-canvas
Readme

react-native-sketch-canvas feature extension

THIS IS A FORK: Added Movable, Scalable and Rotatable Shapes (Geometry shapes and Text Sticker).

New Properties:

  • ShapeConfiguration to set initial shapeBorder color, width and style as well as shapeColor and shapeStrokeWidth
  • AddShapeConfig to indicate what kind of shape to add

New Methods:

  • addShape(config: AddShapeConfig): void
  • deleteSelectedShape(): void
  • increaseSelectedShapeFontsize(): void
  • decreaseSelectedShapeFontsize(): void
  • changeSelectedShapeText(newText: String): void

New Callbacks: onShapeSelectionChanged telling the JS-Side whether or not a shape is selected (to disable JS-Touchlistener)

Check Example1 in the ExampleApp for usage instructions.

react-native-sketch-canvas

A React Native component for drawing by touching on both iOS and Android.

    
    

Features

  • Support iOS and Android
  • Stroke thickness and color are changable while drawing.
  • Can undo strokes one by one.
  • Can serialize path data to JSON. So it can sync other devices or someone else and continue to edit.
  • Save drawing to a non-transparent image (png or jpg) or a transparent image (png only)
  • Use vector concept. So sketches won't be cropped in different sizes of canvas.
  • Support translucent colors and eraser.
  • Support drawing on an image (Thanks to diego-caceres-galvan)
  • High performance (See below. Thanks to jeanregisser)
  • Can draw multiple canvases in the same screen.
  • Can draw multiple multiline text on canvas.

Installation


Install with yarn

yarn add https://github.com/wwimmo/react-native-sketch-canvas.git

Link native code (only required for RN below 0.60)

react-native link @wwimmo/react-native-sketch-canvas

Usage


● Using without UI component (for customizing UI)

import React, { Component } from 'react';
import {
  AppRegistry,
  StyleSheet,
  View,
} from 'react-native';

import { ImageEditor } from '@wwimmo/react-native-sketch-canvas';

export default class example extends Component {
  render() {
    return (
      <View style={styles.container}>
        <View style={{ flex: 1, flexDirection: 'row' }}>
          <ImageEditor
            style={{ flex: 1 }}
            strokeColor={'red'}
            strokeWidth={7}
          />
        </View>
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1, justifyContent: 'center', alignItems: 'center', backgroundColor: '#F5FCFF',
  },
});

AppRegistry.registerComponent('example', () => example);

Properties


PropTypeDescription
styleobjectStyles to be applied on canvas component
strokeColorstringSet the color of stroke, which can be #RRGGBB or #RRGGBBAA. If strokeColor is set to #00000000, it will automatically become an eraser.
NOTE: Once an eraser path is sent to Android, Android View will disable hardware acceleration automatically. It might reduce the canvas performance afterward.
strokeWidthnumberThe thickness of stroke
onStrokeStartfunctionAn optional function which accpets 2 arguments x and y. Called when user's finger touches the canvas (starts to draw)
onStrokeChangedfunctionAn optional function which accpets 2 arguments x and y. Called when user's finger moves
onStrokeEndfunctionAn optional function called when user's finger leaves the canvas (end drawing)
onSketchSavedfunctionAn optional function which accpets 2 arguments success and path. If success is true, image is saved successfully and the saved image path might be in second argument. In Android, image path will always be returned. In iOS, image is saved to camera roll or file system, path will be set to null or image location respectively.
onPathsChangefunctionAn optional function which accpets 1 argument pathsCount, which indicates the number of paths. Useful for UI controls. (Thanks to toblerpwn)
userstringAn identifier to identify who draws the path. Useful when undo between two users
scalenumberSets the scale for the sketchpad, Using the Scale the library returns the paths as per the scale with respect to the sketch canvas dimensions
touchEnabledboolIf false, disable touching. Default is true.
localSourceImageobjectRequire an object (see below) which consists of filename, directory(optional) and mode(optional). If set, the image will be loaded and display as a background in canvas. (Thanks to diego-caceres-galvan))(Here for details)
permissionDialogTitlestringAndroid Only: Provide a Dialog Title for the Image Saving PermissionDialog. Defaults to empty string if not set
permissionDialogMessagestringAndroid Only: Provide a Dialog Message for the Image Saving PermissionDialog. Defaults to empty string if not set

Methods


MethodDescription
clear()Clear all the paths
undo()Delete the latest path. Can undo multiple times.
addPath(path)Add a path (see below) to canvas.
deletePath(id)Delete a path with its id
save(imageType, transparent, folder, filename, includeImage, cropToImageSize)Save image to camera roll or filesystem. If localSourceImage is set and a background image is loaded successfully, set includeImage to true to include background image and set cropToImageSize to true to crop output image to background image.
Android: Save image in imageType format with transparent background (if transparent sets to True) to /sdcard/Pictures/folder/filename (which is Environment.DIRECTORY_PICTURES).
iOS: Save image in imageType format with transparent background (if transparent sets to True) to camera roll or file system. If folder and filename are set, image will save to temporary directory/folder/filename (which is NSTemporaryDirectory())
getPaths()Get the paths that drawn on the canvas
getBase64(imageType, transparent, includeImage, cropToImageSize, callback)Get the base64 of image and receive data in callback function, which called with 2 arguments. First one is error (null if no error) and second one is base64 result.

Constants


ConstantDescription
MAIN_BUNDLEAndroid: empty string, ''
iOS: equivalent to [[NSBundle mainBundle] bundlePath]
DOCUMENTAndroid: empty string, ''
iOS: equivalent to NSDocumentDirectory
LIBRARYAndroid: empty string, ''
iOS: equivalent to NSLibraryDirectory
CACHESAndroid: empty string, ''
iOS: equivalent to NSCachesDirectory

● Using with build-in UI components

import React, { Component } from 'react';
import {
  AppRegistry,
  StyleSheet,
  Text,
  View,
  Alert,
} from 'react-native';

import RNImageEditor from '@wwimmo/react-native-sketch-canvas';

export default class example extends Component {
  render() {
    return (
      <View style={styles.container}>
        <View style={{ flex: 1, flexDirection: 'row' }}>
          <RNImageEditor
            containerStyle={{ backgroundColor: 'transparent', flex: 1 }}
            canvasStyle={{ backgroundColor: 'transparent', flex: 1 }}
            defaultStrokeIndex={0}
            defaultStrokeWidth={5}
            closeComponent={<View style={styles.functionButton}><Text style={{color: 'white'}}>Close</Text></View>}
            undoComponent={<View style={styles.functionButton}><Text style={{color: 'white'}}>Undo</Text></View>}
            clearComponent={<View style={styles.functionButton}><Text style={{color: 'white'}}>Clear</Text></View>}
            eraseComponent={<View style={styles.functionButton}><Text style={{color: 'white'}}>Eraser</Text></View>}
            strokeComponent={color => (
              <View style={[{ backgroundColor: color }, styles.strokeColorButton]} />
            )}
            strokeSelectedComponent={(color, index, changed) => {
              return (
                <View style={[{ backgroundColor: color, borderWidth: 2 }, styles.strokeColorButton]} />
              )
            }}
            strokeWidthComponent={(w) => {
              return (<View style={styles.strokeWidthButton}>
                <View  style={{
                  backgroundColor: 'white', marginHorizontal: 2.5,
                  width: Math.sqrt(w / 3) * 10, height: Math.sqrt(w / 3) * 10, borderRadius: Math.sqrt(w / 3) * 10 / 2
                }} />
              </View>
            )}}
            saveComponent={<View style={styles.functionButton}><Text style={{color: 'white'}}>Save</Text></View>}
            savePreference={() => {
              return {
                folder: 'RNImageEditor',
                filename: String(Math.ceil(Math.random() * 100000000)),
                transparent: false,
                imageType: 'png'
              }
            }}
          />
        </View>
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1, justifyContent: 'center', alignItems: 'center', backgroundColor: '#F5FCFF',
  },
  strokeColorButton: {
    marginHorizontal: 2.5, marginVertical: 8, width: 30, height: 30, borderRadius: 15,
  },
  strokeWidthButton: {
    marginHorizontal: 2.5, marginVertical: 8, width: 30, height: 30, borderRadius: 15,
    justifyContent: 'center', alignItems: 'center', backgroundColor: '#39579A'
  },
  functionButton: {
    marginHorizontal: 2.5, marginVertical: 8, height: 30, width: 60,
    backgroundColor: '#39579A', justifyContent: 'center', alignItems: 'center', borderRadius: 5,
  }
});

AppRegistry.registerComponent('example', () => example);

Properties


PropTypeDescription
containerStyleobjectStyles to be applied on container
canvasStyleobjectStyles to be applied on canvas component
onStrokeStartfunctionSee above
onStrokeChangedfunctionSee above
onStrokeEndfunctionSee above
onPathsChangefunctionSee above
onClosePressedfunctionAn optional function called when user taps closeComponent
onUndoPressedfunctionAn optional function that accepts a argument id (the deleted id of path) and is called when user taps "undo"
onClearPressedfunctionAn optional function called when user taps clearComponent
userstringSee above
closeComponentcomponentAn optional component for closing
eraseComponentcomponentAn optional component for eraser
undoComponentcomponentAn optional component for undoing
clearComponentcomponentAn optional component for clearing
saveComponentcomponentAn optional component for saving
strokeComponentfunctionAn optional function which accpets 1 argument color and should return a component.
strokeSelectedComponentfunctionAn optional function which accpets 3 arguments color, selectedIndex, isColorChanged and should return a component. isColorChanged is useful for animating when changing color. Because rerendering also calls this function, we need isColorChanged to determine whether the component is rerendering or the selected color is changed.
strokeWidthComponentfunctionAn optional function which accpets 1 argument width and should return a component.
strokeColorsarrayAn array of colors. Example: [{ color: '#000000' }, {color: '#FF0000'}]
defaultStrokeIndexnumbberThe default index of selected stroke color
defaultStrokeWidthnumberThe default thickness of stroke
minStrokeWidthnumberThe minimum value of thickness
maxStrokeWidthnumberThe maximum value of thickness
strokeWidthStepnumberThe step value of thickness when tapping strokeWidthComponent.
savePreferencefunctionA function which is called when saving image and should return an object (see below).
onSketchSavedfunctionSee above

Methods


MethodDescription
clear()See above
undo()See above
addPath(path)See above
deletePath(id)See above
save()

Constants


ConstantDescription
MAIN_BUNDLESee above
DOCUMENTSee above
LIBRARYSee above
CACHESSee above

Background Image


To use an image as background, localSourceImage(see below) reqires an object, which consists of filename, directory(optional) and mode(optional).
Note: Because native module cannot read the file in JS bundle, file path cannot be relative to JS side. For example, '../assets/image/image.png' will fail to load image.

Typical Usage

  • Load image from app native bundle
    • Android:
      1. Put your images into android/app/src/main/res/drawable.
      2. Set `filename` to the name of image files with or without file extension. 
      3. Set `directory` to ''
      

    • iOS:
      1. Open Xcode and add images to project by right clicking Add Files to [YOUR PROJECT NAME].
      2. Set filename to the name of image files with file extension.
      3. Set directory to MAIN_BUNDLE (e.g. RNImageEditor.MAIN_BUNDLE or ImageEditor.MAIN_BUNDLE)
  • Load image from camera
    1. Retrive photo complete path (including file extension) after snapping.
    2. Set filename to that path.
    3. Set directory to ''

Content Mode

  • AspectFill
  • AspectFit (default)
  • ScaleToFill

Objects


SavePreference object

{
  folder: 'RNImageEditor',
  filename: 'image',
  transparent: true,
  imageType: 'jpg',
  includeImage: true,
  includeText: false,
  cropToImageSize: true
}
PropertyTypeDescription
folder?stringAndroid: the folder name in Pictures directory
iOS: if filename is not null, image will save to temporary directory with folder and filename, otherwise, it will save to camera roll
filename?stringthe file name of image
iOS: Set to null to save image to camera roll.
transparentbooleansave canvas with transparent background, ignored if imageType is jpg
imageTypestringimage file format
Options: png, jpg
includeImage?booleanSet to true to include the image loaded from LocalSourceImage. (Default is true)
includeImage?booleanSet to true to include the text drawn from Text. (Default is true)
cropToImageSize?booleanSet to true to crop output image to the image loaded from LocalSourceImage. (Default is false)

Path object

{
  drawer: 'user1',
  size: { // the size of drawer's canvas
    width: 480,
    height: 640
  },
  path: {
    id: 8979841, // path id
    color: '#FF000000', // ARGB or RGB
    width: 5,
    data: [
      "296.11,281.34",  // x,y
      "293.52,284.64",
      "290.75,289.73"
    ]
  }
}

LocalSourceImage object

{
  filename: 'image.png',  // e.g. 'image.png' or '/storage/sdcard0/Pictures/image.png'
  directory: '', // e.g. ImageEditor.MAIN_BUNDLE or '/storage/sdcard0/Pictures/'
  mode: 'AspectFill'
}
PropertyTypeDescriptionDefault
filenamestringthe fold name of the background image file (can be a full path)
directory?stringthe directory of the background image file (usually used with constants)''
mode?booleanSpecify how the background image resizes itself to fit or fill the canvas.
Options: AspectFill, AspectFit, ScaleToFill
AspectFit

CanvasText object

{
  text: 'TEXT',
  font: '',
  fontSize: 20,
  fontColor: 'red',
  overlay: 'TextOnSketch',
  anchor: { x: 0, y: 1 },
  position: { x: 100, y: 200 },
  coordinate: 'Absolute',
  alignment: 'Center',
  lineHeightMultiple: 1.2
}
PropertyTypeDescriptionDefault
textstringthe text to display (can be multiline by \n)
font?stringAndroid: You can set font to fonts/[filename].ttf to load font in android/app/src/main/assets/fonts/ in your Android project
iOS: Set font that included with iOS
fontSize?numberfont size12
fontColor?stringtext colorblack
overlay?stringSet to TextOnSketch to overlay drawing with text, otherwise the text will be overlaid with drawing.
Options: TextOnSketch, SketchOnText
SketchOnText
anchor?objectSet the origin point of the image. (0, 0) to (1, 1). (0, 0) and (1, 1) indicate the top-left and bottom-right point of the image respectively.{ x: 0, y: 0 }
positionobjectSet the position of the image on canvas. If coordinate is Ratio, (0, 0) and (1, 1) indicate the top-left and bottom-right point of the canvas respectively.{ x: 0, y: 0 }
coordinate?stringSet to Absolute and Ratio to treat position as absolute position (in point) and proportion respectively.
Options: Absolute, Ratio
Absolute
alignment?stringSpecify how the text aligns inside container. Only work when text is multiline text.Left
lineHeightMultiple?numberMultiply line height by this factor. Only work when text is multiline text.1.0

Performance


  1. For non-transparent path, both Android and iOS performances are good. Because when drawing non-transparent path, only last segment is drawn on canvas, no matter how long the path is, CPU usage is stable at about 20% and 15% in Android and iOS respectively.
  2. For transparent path, CPU usage stays at around 25% in Android, however, in iOS, CPU usage grows to 100% :(.

Example


The source code includes 3 examples, using build-in UI components, using with only canvas, and sync between two canvases.

Check full example app in the example folder

Troubleshooting


Please refer here.