import { Dimensions } from "react-native";
const win = Dimensions.get('window');
<Image
style={{
width: win.width/2,
height: win.width/2,
resizeMode: "contain",
alignSelf: "center",
borderWidth: 1,
borderRadius: 20,
}}
source={{uri:'https://facebook.github.io/react/img/logo_og.png'}}
resizeMode="stretch"
/>