How to set image width to be 100% and height to be auto in react native?

So after thinking for a while I was able to achieve height: auto in react-native image.
You need to know the dimensions of your image for this hack to work. Just open your image in any image viewer and you will get the dimensions of the your image in file information.
For reference the size of image I used is 541 x 362

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
}