You can use ML Kit to recognize and decode barcodes.
Before you begin
- If you haven't already, add Firebase to your Android project .
- Add the dependencies for the ML Kit Android libraries to your module
(app-level) Gradle file (usually
app/build.gradle):apply plugin : ' com . android . application ' apply plugin : ' com . google . gms . google - services ' dependencies { // ... implementation ' com . google . firebase : firebase - ml - vision : 24.0.3 ' implementation ' com . google . firebase : firebase - ml - vision - barcode - model : 16.0.1 ' }
Input image guidelines
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For ML Kit to accurately read barcodes, input images must contain barcodes that are represented by sufficient pixel data.
The specific pixel data requirements are dependent on both the type of barcode and the amount of data that is encoded in it (since most barcodes support a variable length payload). In general, the smallest meaningful unit of the barcode should be at least 2 pixels wide (and for 2-dimensional codes, 2 pixels tall).
For example, EAN-13 barcodes are made up of bars and spaces that are 1, 2, 3, or 4 units wide, so an EAN-13 barcode image ideally has bars and spaces that are at least 2, 4, 6, and 8 pixels wide. Because an EAN-13 barcode is 95 units wide in total, the barcode should be at least 190 pixels wide.
Denser formats, such as PDF417, need greater pixel dimensions for ML Kit to reliably read them. For example, a PDF417 code can have up to 34 17-unit wide "words" in a single row, which would ideally be at least 1156 pixels wide.
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Poor image focus can hurt scanning accuracy. If you aren't getting acceptable results, try asking the user to recapture the image.
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For typical applications, it is recommended to provide a higher resolution image (such as 1280x720 or 1920x1080), which makes barcodes detectable from a larger distance away from the camera.
However, in applications where latency is critical, you can improve performance by capturing images at a lower resolution, but requiring that the barcode make up the majority of the input image. Also see Tips to improve real-time performance .
1. Configure the barcode detector
If you know which barcode formats you expect to read, you can improve the speed of the barcode detector by configuring it to only detect those formats.For example, to detect only Aztec code and QR codes, build a FirebaseVisionBarcodeDetectorOptions
object as in the following example:
Java
FirebaseVisionBarcodeDetectorOptions options = new FirebaseVisionBarcodeDetectorOptions . Builder () . setBarcodeFormats ( FirebaseVisionBarcode . FORMAT_QR_CODE , FirebaseVisionBarcode . FORMAT_AZTEC ) . build ();
Kotlin
val options = FirebaseVisionBarcodeDetectorOptions . Builder () . setBarcodeFormats ( FirebaseVisionBarcode . FORMAT_QR_CODE , FirebaseVisionBarcode . FORMAT_AZTEC ) . build ()
The following formats are supported:
- Code 128 (
FORMAT_CODE_128) - Code 39 (
FORMAT_CODE_39) - Code 93 (
FORMAT_CODE_93) - Codabar (
FORMAT_CODABAR) - EAN-13 (
FORMAT_EAN_13) - EAN-8 (
FORMAT_EAN_8) - ITF (
FORMAT_ITF) - UPC-A (
FORMAT_UPC_A) - UPC-E (
FORMAT_UPC_E) - QR Code (
FORMAT_QR_CODE) - PDF417 (
FORMAT_PDF417) - Aztec (
FORMAT_AZTEC) - Data Matrix (
FORMAT_DATA_MATRIX)
2. Run the barcode detector
To recognize barcodes in an image, create aFirebaseVisionImage
object
from either a Bitmap
, media.Image
, ByteBuffer
, byte array, or a file on
the device. Then, pass the FirebaseVisionImage
object to the FirebaseVisionBarcodeDetector
's detectInImage
method. -
Create a
FirebaseVisionImageobject from your image.-
To create a
FirebaseVisionImageobject from amedia.Imageobject, such as when capturing an image from a device's camera, pass themedia.Imageobject and the image's rotation toFirebaseVisionImage.fromMediaImage().If you use the CameraX library, the
OnImageCapturedListenerandImageAnalysis.Analyzerclasses calculate the rotation value for you, so you just need to convert the rotation to one of ML Kit'sROTATION_constants before callingFirebaseVisionImage.fromMediaImage():Java
private class YourAnalyzer implements ImageAnalysis . Analyzer { private int degreesToFirebaseRotation ( int degrees ) { switch ( degrees ) { case 0 : return FirebaseVisionImageMetadata . ROTATION_0 ; case 90 : return FirebaseVisionImageMetadata . ROTATION_90 ; case 180 : return FirebaseVisionImageMetadata . ROTATION_180 ; case 270 : return FirebaseVisionImageMetadata . ROTATION_270 ; default : throw new IllegalArgumentException ( "Rotation must be 0, 90, 180, or 270." ); } } @Override public void analyze ( ImageProxy imageProxy , int degrees ) { if ( imageProxy == null || imageProxy . getImage () == null ) { return ; } Image mediaImage = imageProxy . getImage (); int rotation = degreesToFirebaseRotation ( degrees ); FirebaseVisionImage image = FirebaseVisionImage . fromMediaImage ( mediaImage , rotation ); // Pass image to an ML Kit Vision API // ... } }
Kotlin
private class YourImageAnalyzer : ImageAnalysis . Analyzer { private fun degreesToFirebaseRotation ( degrees : Int ): Int = when ( degrees ) { 0 -> FirebaseVisionImageMetadata . ROTATION_0 90 -> FirebaseVisionImageMetadata . ROTATION_90 180 -> FirebaseVisionImageMetadata . ROTATION_180 270 -> FirebaseVisionImageMetadata . ROTATION_270 else -> throw Exception ( "Rotation must be 0, 90, 180, or 270." ) } override fun analyze ( imageProxy : ImageProxy?, degrees : Int ) { val mediaImage = imageProxy ?. image val imageRotation = degreesToFirebaseRotation ( degrees ) if ( mediaImage != null ) { val image = FirebaseVisionImage . fromMediaImage ( mediaImage , imageRotation ) // Pass image to an ML Kit Vision API // ... } } }
If you don't use a camera library that gives you the image's rotation, you can calculate it from the device's rotation and the orientation of camera sensor in the device:
Java
private static final SparseIntArray ORIENTATIONS = new SparseIntArray (); static { ORIENTATIONS . append ( Surface . ROTATION_0 , 90 ); ORIENTATIONS . append ( Surface . ROTATION_90 , 0 ); ORIENTATIONS . append ( Surface . ROTATION_180 , 270 ); ORIENTATIONS . append ( Surface . ROTATION_270 , 180 ); } /** * Get the angle by which an image must be rotated given the device's current * orientation. */ @RequiresApi ( api = Build . VERSION_CODES . LOLLIPOP ) private int getRotationCompensation ( String cameraId , Activity activity , Context context ) throws CameraAccessException { // Get the device's current rotation relative to its "native" orientation. // Then, from the ORIENTATIONS table, look up the angle the image must be // rotated to compensate for the device's rotation. int deviceRotation = activity . getWindowManager (). getDefaultDisplay (). getRotation (); int rotationCompensation = ORIENTATIONS . get ( deviceRotation ); // On most devices, the sensor orientation is 90 degrees, but for some // devices it is 270 degrees. For devices with a sensor orientation of // 270, rotate the image an additional 180 ((270 + 270) % 360) degrees. CameraManager cameraManager = ( CameraManager ) context . getSystemService ( CAMERA_SERVICE ); int sensorOrientation = cameraManager . getCameraCharacteristics ( cameraId ) . get ( CameraCharacteristics . SENSOR_ORIENTATION ); rotationCompensation = ( rotationCompensation + sensorOrientation + 270 ) % 360 ; // Return the corresponding FirebaseVisionImageMetadata rotation value. int result ; switch ( rotationCompensation ) { case 0 : result = FirebaseVisionImageMetadata . ROTATION_0 ; break ; case 90 : result = FirebaseVisionImageMetadata . ROTATION_90 ; break ; case 180 : result = FirebaseVisionImageMetadata . ROTATION_180 ; break ; case 270 : result = FirebaseVisionImageMetadata . ROTATION_270 ; break ; default : result = FirebaseVisionImageMetadata . ROTATION_0 ; Log . e ( TAG , "Bad rotation value: " + rotationCompensation ); } return result ; }
Kotlin
private val ORIENTATIONS = SparseIntArray () init { ORIENTATIONS . append ( Surface . ROTATION_0 , 90 ) ORIENTATIONS . append ( Surface . ROTATION_90 , 0 ) ORIENTATIONS . append ( Surface . ROTATION_180 , 270 ) ORIENTATIONS . append ( Surface . ROTATION_270 , 180 ) } /** * Get the angle by which an image must be rotated given the device's current * orientation. */ @RequiresApi ( api = Build . VERSION_CODES . LOLLIPOP ) @Throws ( CameraAccessException :: class ) private fun getRotationCompensation ( cameraId : String , activity : Activity , context : Context ): Int { // Get the device's current rotation relative to its "native" orientation. // Then, from the ORIENTATIONS table, look up the angle the image must be // rotated to compensate for the device's rotation. val deviceRotation = activity . windowManager . defaultDisplay . rotation var rotationCompensation = ORIENTATIONS . get ( deviceRotation ) // On most devices, the sensor orientation is 90 degrees, but for some // devices it is 270 degrees. For devices with a sensor orientation of // 270, rotate the image an additional 180 ((270 + 270) % 360) degrees. val cameraManager = context . getSystemService ( CAMERA_SERVICE ) as CameraManager val sensorOrientation = cameraManager . getCameraCharacteristics ( cameraId ) . get ( CameraCharacteristics . SENSOR_ORIENTATION ) !! rotationCompensation = ( rotationCompensation + sensorOrientation + 270 ) % 360 // Return the corresponding FirebaseVisionImageMetadata rotation value. val result : Int when ( rotationCompensation ) { 0 - > result = FirebaseVisionImageMetadata . ROTATION_0 90 - > result = FirebaseVisionImageMetadata . ROTATION_90 180 - > result = FirebaseVisionImageMetadata . ROTATION_180 270 - > result = FirebaseVisionImageMetadata . ROTATION_270 else - > { result = FirebaseVisionImageMetadata . ROTATION_0 Log . e ( TAG , "Bad rotation value: $ rotationCompensation " ) } } return result }
Then, pass the
media.Imageobject and the rotation value toFirebaseVisionImage.fromMediaImage():Java
FirebaseVisionImage image = FirebaseVisionImage . fromMediaImage ( mediaImage , rotation );
Kotlin
val image = FirebaseVisionImage . fromMediaImage ( mediaImage , rotation )
- To create a
FirebaseVisionImageobject from a file URI, pass the app context and file URI toFirebaseVisionImage.fromFilePath(). This is useful when you use anACTION_GET_CONTENTintent to prompt the user to select an image from their gallery app.Java
FirebaseVisionImage image ; try { image = FirebaseVisionImage . fromFilePath ( context , uri ); } catch ( IOException e ) { e . printStackTrace (); }
Kotlin
val image : FirebaseVisionImage try { image = FirebaseVisionImage . fromFilePath ( context , uri ) } catch ( e : IOException ) { e . printStackTrace () }
- To create a
FirebaseVisionImageobject from aByteBufferor a byte array, first calculate the image rotation as described above formedia.Imageinput.Then, create a
FirebaseVisionImageMetadataobject that contains the image's height, width, color encoding format, and rotation:Java
FirebaseVisionImageMetadata metadata = new FirebaseVisionImageMetadata . Builder () . setWidth ( 480 ) // 480x360 is typically sufficient for . setHeight ( 360 ) // image recognition . setFormat ( FirebaseVisionImageMetadata . IMAGE_FORMAT_NV21 ) . setRotation ( rotation ) . build ();
Kotlin
val metadata = FirebaseVisionImageMetadata . Builder () . setWidth ( 480 ) // 480x360 is typically sufficient for . setHeight ( 360 ) // image recognition . setFormat ( FirebaseVisionImageMetadata . IMAGE_FORMAT_NV21 ) . setRotation ( rotation ) . build ()
Use the buffer or array, and the metadata object, to create a
FirebaseVisionImageobject:Java
FirebaseVisionImage image = FirebaseVisionImage . fromByteBuffer ( buffer , metadata ); // Or: FirebaseVisionImage image = FirebaseVisionImage.fromByteArray(byteArray, metadata);
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