Answers for "how to fit an image to screen in react native"

react native cover image

// You want `resizeMode`
The options are 'cover' | 'contain' | 'stretch' | 'repeat' | 'center'
     
<Image
  style={{
    width: size,
    height: size,
    resizeMode: "contain", // <--
  }}
  source={...}
/>

react native image fit container

<Image
  style={{
    alignSelf: 'center',
    height: 150,
    width: 150,
    borderWidth: 1,
    borderRadius: 75
  }}
  source={{uri:'https://facebook.github.io/react/img/logo_og.png'}}
  resizeMode="stretch"
/>
// source: https://medium.com/the-react-native-log/tips-for-react-native-images-or-saying-goodbye-to-trial-and-error-b2baaf0a1a4d