그다음엔 CameraButton의 onPickImage 함수에서 방금 만든 포스트 작성 화면의 res 값을 라우트 파라미터로 넣어서 열어주세요.

components/CameraButton.js

(...)
import {useNavigation} from '@react-navigation/native';

const TABBAR_HEIGHT = 49;

const imagePickerOption = {
  mediaType: 'photo',
  maxWidth: 768,
  maxHeight: 768,
  includeBase64: Platform.OS === 'android',
};

function CameraButton() {
  const insets = useSafeAreaInsets();
  const [modalVisible, setModalVisible] = useState(false);
  const navigation = useNavigation();

  const bottom = Platform.select({
    android: TABBAR_HEIGHT / 2,
    ios: TABBAR_HEIGHT / 2 + insets.bottom - 4,
  });

  const onPickImage = (res) => {
    if (res.didCancel || !res) {
      return;
    }
    navigation.push('Upload', {res});
  };

(...)