這是我用于條碼掃描的精簡源代碼
構建.gradle
dependencies {
.....
// MLKit Dependencies
implementation 'com.google.android.gms:play-services-vision:20.1.3'
implementation 'com.google.mlkit:barcode-scanning:17.0.2'
def camerax_version = "1.1.0-beta01"
implementation "androidx.camera:camera-core:${camerax_version}"
implementation "androidx.camera:camera-camera2:${camerax_version}"
implementation "androidx.camera:camera-lifecycle:${camerax_version}"
implementation "androidx.camera:camera-video:${camerax_version}"
......
}
ScanCameraFragment.kt
class ScanCameraFragment : BaseFragment() {
private lateinit var binding: FragmentScanCameraBinding
private lateinit var cameraExecutor: ExecutorService
//region Lifecycle Methods
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
binding = FragmentScanCameraBinding.inflate(inflater, container, false)
cameraExecutor = Executors.newSingleThreadExecutor()
startCamera()
return binding.root
}
override fun onDestroyView() {
super.onDestroyView()
cameraExecutor.shutdown()
}
companion object {
fun newInstance() = ScanCameraFragment().apply {}
}
private fun startCamera() {
context?.let { context ->
val cameraProviderFuture = ProcessCameraProvider.getInstance(context)
cameraProviderFuture.addListener({
val cameraProvider = cameraProviderFuture.get()
// Preview
val preview = Preview.Builder()
.build()
.also {
it.setSurfaceProvider(binding.previewView.surfaceProvider)
}
// Image analyzer
val imageAnalyzer = ImageAnalysis.Builder()
.setBackpressureStrategy(ImageAnalysis.STRATEGY_KEEP_ONLY_LATEST)
.build()
.also {
it.setAnalyzer(cameraExecutor,
QrCodeAnalyzer(context, binding.barcodeBoxView,
binding.previewView.width.toFloat(),
binding.previewView.height.toFloat()
)
)
}
// Select back camera as a default
val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA
try {
// Unbind use cases before rebinding
cameraProvider.unbindAll()
// Bind use cases to camera
var camera = cameraProvider.bindToLifecycle(this, cameraSelector,
preview, imageAnalyzer)
} catch (exc: Exception) {
exc.printStackTrace()
}
}, ContextCompat.getMainExecutor(context))
}
}
}
二維碼分析器.kt
class QrCodeAnalyzer(private val context: Context,
private val barcodeBoxView: BarcodeBoxView, private val previewViewWidth: Float,
private val previewViewHeight: Float) : ImageAnalysis.Analyzer {
private var scaleX = 1f
private var scaleY = 1f
private fun translateX(x: Float) = x * scaleX
private fun translateY(y: Float) = y * scaleY
private fun adjustBoundingRect(rect: Rect) = RectF(
translateX(rect.left.toFloat()),
translateY(rect.top.toFloat()),
translateX(rect.right.toFloat()),
translateY(rect.bottom.toFloat())
)
@SuppressLint("UnsafeOptInUsageError")
override fun analyze(image: ImageProxy) {
val img = image.image
if (img != null) {
// Update scale factors
scaleX = previewViewWidth / img.height.toFloat()
scaleY = previewViewHeight / img.width.toFloat()
val inputImage = InputImage.fromMediaImage(img,
image.imageInfo.rotationDegrees)
// Process image searching for barcodes
val options = BarcodeScannerOptions.Builder()
.build()
val scanner = BarcodeScanning.getClient(options)
scanner.process(inputImage)
.addOnSuccessListener { barcodes ->
for (barcode in barcodes) {
barcode?.rawValue?.let {
if (it.trim().isNotBlank()) {
Scanner.updateBarcode(it)
barcode.boundingBox?.let { rect ->
barcodeBoxView.setRect(adjustBoundingRect(rect))
}
}
return@addOnSuccessListener
}
}
// coming here means no satisfiable barcode was found
barcodeBoxView.setRect(RectF())
}
.addOnFailureListener {
image.close()
}
.addOnFailureListener { }
}
image.close()
}
}
此代碼有效，我能夠掃描條形碼。但有時，條碼檢測速度很慢。檔案說提高性能的一種方法是限制影像解析度。
不要以相機的原始解析度捕獲輸入。在某些設備上，以原始解析度捕獲輸入會產生非常大的（10 百萬像素）影像，這會導致非常差的延遲，并且不會提高準確性。相反，只向相機請求條碼檢測所需的尺寸，通常不超過 2 兆像素。
如果掃描速度很重要，您可以進一步降低影像捕獲解析度。但是，請記住上述最低條碼尺寸要求。
不幸的是，檔案沒有說明如何降低影像解析度。我的一些最終用戶正在使用配備強大攝像頭的高端設備，因此我們認為性能不佳是因為影像大小。
如何將影像的解析度降低到固定值（例如 1024 x 768）而不是默認的相機解析度？
uj5u.com熱心網友回復：
您可以使用 .setTargetResolution(Size) 在 imageAnalyzer builder bij 上設定它
val imageAnalysisUseCaseBuilder = ImageAnalysis.Builder()
imageAnalysisUseCaseBuilder.setTargetResolution(Size(1024, 768))
imageAnalysisUseCase = imageAnalysisUseCaseBuilder.build()
或者在你的情況下
val imageAnalyzer = ImageAnalysis.Builder()
.setTargetResolution(Size(1024, 768))
.setBackpressureStrategy(ImageAnalysis.STRATEGY_KEEP_ONLY_LATEST)
.build()
.also {
it.setAnalyzer(cameraExecutor,
QrCodeAnalyzer(context, binding.barcodeBoxView,
binding.previewView.width.toFloat(),
binding.previewView.height.toFloat()
)
)
}
uj5u.com熱心網友回復：
用戶 HarmenH 的回答正確地告訴了如何設定影像解析度，所以我在這里不再重復。
事實證明，我的性能問題不是因為影像解析度。看來我過早地關閉了 imageProxy。
override fun analyze(image: ImageProxy) {
val img = image.image
if (img != null) {
// Update scale factors
scaleX = previewViewWidth / img.height.toFloat()
scaleY = previewViewHeight / img.width.toFloat()
val inputImage = InputImage.fromMediaImage(img,
image.imageInfo.rotationDegrees)
// Process image searching for barcodes
val options = BarcodeScannerOptions.Builder()
.build()
val scanner = BarcodeScanning.getClient(options)
scanner.process(inputImage)
.addOnSuccessListener { barcodes - >
for (barcode in barcodes) {
barcode?.rawValue?.let {
if (it.trim().isNotBlank()) {
Scanner.updateBarcode(it)
barcode.boundingBox?.let { rect - >
barcodeBoxView.setRect(adjustBoundingRect(rect))
}
}
return @addOnSuccessListener
}
}
// coming here means no satisfiable barcode was found
barcodeBoxView.setRect(RectF())
}
.addOnFailureListener {
image.close()
}
.addOnFailureListener {
//added this here.
image.close()
}
}
//Removed this because we don't close the
//imageProxy before analysis completes
//image.close()
}
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