react-native-image-crop-picker/example/app.js

import React, {Component} from 'react';
import {View, Text, StyleSheet, ScrollView, Image, TouchableOpacity} from 'react-native';

import {NativeModules} from 'react-native';
var ImagePicker = NativeModules.ImageCropPicker;

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center'
  },
  button: {
    backgroundColor: 'blue',
    marginBottom: 10
  },
  text: {
    color: 'white',
    fontSize: 20
  }
});

export default class App extends Component {

  constructor() {
    super();
    this.state = {
      image: null,
      images: null
    };
  }

  pickSingle(cropit) {
    ImagePicker.openPicker({
      width: 300,
      height: 300,
      cropping: cropit
    }).then(image => {
      console.log('received image', image);
      this.setState({
        image: {uri: image.path, width: image.width, height: image.height},
        images: null
      });
    }).catch(e => {});
  }

  pickMultiple() {
    ImagePicker.openPicker({
      multiple: true
    }).then(images => {
      this.setState({
        image: null,
        images: images.map(i => {
          console.log('received image', i);
          return {uri: i.path, width: i.width, height: i.height};
        })
      });
    }).catch(e => {});
  }

  scaledHeight(oldW, oldH, newW) {
    return (oldH / oldW) * newW;
  }

  render() {
    return <View style={styles.container}>

      <ScrollView>
        {this.state.image ? <Image style={{width: this.state.image.width, height: this.state.image.height}} source={this.state.image} /> : null}
        {this.state.images ? this.state.images.map(i => <Image key={i.uri} style={{width: 300, height: this.scaledHeight(i.width, i.height, 300)}} source={i} />) : null}
      </ScrollView>

      <TouchableOpacity onPress={() => this.pickSingle(false)} style={styles.button}>
        <Text style={styles.text}>Select Single</Text>
      </TouchableOpacity>
      <TouchableOpacity onPress={() => this.pickSingle(true)} style={styles.button}>
        <Text style={styles.text}>Select Single With Cropping</Text>
      </TouchableOpacity>
      <TouchableOpacity onPress={this.pickMultiple.bind(this)} style={styles.button}>
        <Text style={styles.text}>Select Multiple</Text>
      </TouchableOpacity>
    </View>;
  }
}