Barcode scanner returns different strings in Android an iOS when scanning a UPC-A format code

[nthchild1]

What's happening?

I am trying to scan upc-a (12 digit) codes which are not directly supported by this library. However, this library does support ean-13 which is a superset standard with an extra digit (13 digit). You can convert any upc-a code to an ean-13 code by just adding a zero to the beginning of the string.

The problem is that, when scanning an upc-a code with the ean-13 codeType enabled, the scanner returns a 13 digit ean-13 code as expected for iOS (it is adding an extra zero to the start of the string). It seems that in Android it is not adding a zero to the start of the string and is returning the original 12 digit code, resulting string is different for each platform.

For example:

Scanning the following code:

returns 050000463916 in Android and 0050000463916 in iOS

Reproduceable Code

import 'react-native-reanimated';
import React, { useEffect } from 'react';
import { StyleSheet, View } from 'react-native';
import { useIsFocused } from '@react-navigation/native';
import { Camera, useCameraDevice, useCodeScanner } from 'react-native-vision-camera';

const ScannerScreen = () => {
  const isFocused = useIsFocused();
  const device = useCameraDevice('back');

  const codeScanner = useCodeScanner({
    codeTypes: ['ean-13'],
    onCodeScanned: (codes) => {
      console.log(codes);
    },
  });

  useEffect(() => {
    void Camera.getCameraPermissionStatus();
  }, []);

  return (
    <>
      <View style={{ flex: 1 }}>
        {isFocused && device && (
          <Camera
            style={StyleSheet.absoluteFillObject}
            device={device}
            isActive={!!device}
            codeScanner={codeScanner}
          />
        )}
      </View>
    </>
  );
};

export default ScannerScreen;

Relevant log output

No logs

Camera Device

Any camera device

Device

Any iOS or Android smartphone

VisionCamera Version

3.3.1

Can you reproduce this issue in the VisionCamera Example app?

Yes, I can reproduce the same issue in the Example app here

Additional information

• [ ] I am using Expo
• [ ] I have enabled Frame Processors (react-native-worklets-core)
• [X] I have read the Troubleshooting Guide
• [X] I agree to follow this project's Code of Conduct
• [X] I searched for similar issues in this repository and found none.

[gary-cohen]

Yes, it would be nice if the lib supported upc-a especially since BarcodeScannerOptions supports it.

[Gambitboy]

Same, I also need ability to scan upc_a, coming from vision-camera-code-scanner which was deprecated in favour of v3

[jimsideout]

Same issue. Seems clunky to need to remove the leading 0 in iOS.

[Gambitboy]

I managed to get this working by modifying the android files to include upc-a and running patch-package. iOS already has the ability to scan upc-a because of ean-13, I just do a check to include the extra digit.

[marcshilling]

@Gambitboy can you share your patch file please?

[Gambitboy]

@marcshilling Here is the patch file. Its quite a big. Not sure why, as it wasn't a lot of changes. I still have a type issue for upc-a which I haven't resolved yet.

https://gist.github.com/Gambitboy/0a2afa2485fd7c285a52b093de1c32b2

[arisyo13]

I have a similar issue. On android it can scan multiple barcodes and returns an array with all the barcodes scanned but on ios it returns only one item inside the array.

[mrousavy]

On iOS I use the native QR scanner from Apple, on Android I use Google's MLKit model. If there are differences, there's nothing I can do.

You can instead write a custom Frame Processor Plugin to use the same libs on both devices, or something like ZXing.

[Couzix]

Hi ! MLKit actually provides support for upc-a ! "The following formats are supported: [...] UPC-A (FORMAT_UPC_A)". Sorry for tagging you @mrousavy, but do you consider in supporting it in your lib ? Thanks a lot !!

[mrousavy]

Hey @Couzix - Apple's Vision library doesn't support UPC-A though, so it would not be a cross-platform feature, which I like to avoid.

[Gambitboy]

When I read through the apple docs it said it indirectly supported upc-a through ean. So once I added the missing code for android both devices types were able to scan a upc-a code.

[mrousavy]

Oh, interesting. Well I guess I could add those types and just mark them as @platform Android then..

[Gambitboy]

I'll quickly try to find the docs mentioning it, also since its working on my project. I don't mind doing a pull request. The only bit I never got to finish was type checking the UPC-A for android

[Gambitboy]

I think it was here.