First import Dimensions from react-native

import { Dimensions } from 'react-native';
then you have to get the dimensions of the window

const win = Dimensions.get('window');
Now calculate ratio as

const ratio = win.width/541; //541 is actual image width
now the add style to your image as

imageStyle: {
    width: win.width,
    height: 362 * ratio, //362 is actual height of image
}