CODE EXAMPLE FOR JAVASCRIPT

react native onChangeText resize the background image

const d = Dimensions.get("window")

backgroundImage: {
  position: 'absolute'
  flex: 1,
  backgroundColor:'rgba(0,0,0,0.45)',
  width: d.width,
  height: d.height
}

<ImageBackground 
source={require('../../assets/signinBG.jpg')} 
style={styles.backgroundImage}
resizeMode="repeat" // or contain or cover
>