CameraX 使 ImageAnalysis 的大小与 Preview 相同

Question

I want to be able to get the exact image for analysis step as I get in preview. I have preview use case:

val metrics = DisplayMetrics().also { binding.codeScannerView.display.getRealMetrics(it) }
    val screenAspectRatio = Rational(metrics.widthPixels, metrics.heightPixels)
    val previewConfig = PreviewConfig.Builder().apply {
        setTargetAspectRatio(screenAspectRatio)
    }.build()

And next to it I have analysis use case config:

val analyzerConfig = ImageAnalysisConfig.Builder().apply {
        setTargetResolution(Size(metrics.heightPixels, metrics.widthPixels))
        setTargetAspectRatio(screenAspectRatio)
        val analyzerThread = HandlerThread(
                "QrCodeReader").apply { start() }
        setCallbackHandler(Handler(analyzerThread.looper))
        setImageReaderMode(
                ImageAnalysis.ImageReaderMode.ACQUIRE_LATEST_IMAGE)
    }.build()

My preview is fullscreen so it's size is 1440x2560. But if I try to get dimensions from ImageProxy in analyzer, I get 1920x1050 which seems to have incorrect dimensions and switched width with height. Why is that and how can I force my analysis step to have same dimensions as full screen?

Answer 1

Intro:

implementation 'androidx.camera:camera-core:1.0.0-alpha10'
implementation 'androidx.camera:camera-camera2:1.0.0-alpha10'
implementation "androidx.camera:camera-lifecycle:1.0.0-alpha10"
implementation "androidx.camera:camera-view:1.0.0-alpha07"
implementation 'com.google.firebase:firebase-ml-vision:24.0.1'
implementation 'com.google.firebase:firebase-ml-vision-barcode-model:16.0.2'

I am solve this issue via the method FirebaseVisionImage.fromBitmap(bitmap) where bitmap - manual cropped && rotated image according to preview configuration. The steps are:

1. when you setup ImageAnalysis.Builder() && Preview.Builder() obtain the on-screen rendered size for androidx.camera.view.PreviewView element:

    previewView.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED) val previewSize = Size(previewView.width, previewView.height)

   Then pass the size into your own ImageAnalysis.Analyzer implementation (let's say it will be viewFinderSize variable, usage see below)

2. when override fun analyze(mediaImage: ImageProxy){ occurs, do the manual crop of received ImageProxy . I am use the snippet from another SO question about distorted YUV_420_888 image: https://stackoverflow.com/a/45926852/2118862

When you do the cropping, keep in mind that ImageAnalysis use case receive image aligned in vertical-middle basis within your preview use case. In other words, received image, after rotation will be vertically centred as if it will be inside your preview area (even if your preview area is smaller than the image passed into analysis). So, crop area should be calculated in both directions from the vertical center: up and down.

The vertical size of the crop (height) should be manually calculated on the horizontal size basis. This means, when you receive image into analysis, it has full horizontal size within your preview area (100% of width inside preview is equal 100% of width inside analysis). So, no hidden zones in horizontal dimension. This open the way to calculate the size for vertical cropping. I am done this with next code:

var bitmap = ... <- obtain the bitmap as suggested in the SO link above
val matrix = Matrix()
matrix.postRotate(90f)
bitmap = Bitmap.createBitmap(bitmap, 0, 0, image.width, image.height, matrix, true)
val cropHeight = if (bitmap.width < viewFinderSize!!.width) {
    // if preview area larger than analysing image
    val koeff = bitmap.width.toFloat() / viewFinderSize!!.width.toFloat()
    viewFinderSize!!.height.toFloat() * koeff
} else {
    // if preview area smaller than analysing image
    val prc = 100 - (viewFinderSize!!.width.toFloat()/(bitmap.width.toFloat()/100f))
    viewFinderSize!!.height + ((viewFinderSize!!.height.toFloat()/100f) * prc)
}

val cropTop = (bitmap.height/2)-((cropHeight)/2)
bitmap = Bitmap.createBitmap(bitmap, 0, cropTop.toInt(), bitmap.width, cropHeight.toInt())

The final value in bitmap variable - is the cropped image ready to pass into FirebaseVisionImage.fromBitmap(bitmap)

PS. welcome to improve the suggested variant

Answer 2

May be I am late but here is the code working for me

Few times if the the cropTop comes as -ve value so whenever the negative value comes you should process image which comes from ImageProxy in other cases you can process cropped bitmap

        val mediaImage = imageProxy.image ?: return
        var bitmap = ImageUtils.convertYuv420888ImageToBitmap(mediaImage)

        val rotationDegrees = imageProxy.imageInfo.rotationDegrees

        val matrix = Matrix()
        matrix.postRotate(rotationDegrees.toFloat())

        bitmap =
            Bitmap.createBitmap(bitmap, 0, 0, mediaImage.width, mediaImage.height, matrix, true)
        val cropHeight = if (bitmap.width < previewView.width) {
            // if preview area larger than analysing image
            val koeff = bitmap.width.toFloat() / previewView.width.toFloat()
            previewView.height.toFloat() * koeff
        } else {
            // if preview area smaller than analysing image
            val prc = 100 - (previewView.width.toFloat() / (bitmap.width.toFloat() / 100f))
            previewView.height + ((previewView.height.toFloat() / 100f) * prc)
        }

        val cropTop = (bitmap.height / 2) - ((cropHeight) / 2)

        if (cropTop > 0) {
            Bitmap.createBitmap(bitmap, 0, cropTop.toInt(), bitmap.width, cropHeight.toInt())
                .also { process(it, imageProxy) }
        } else {
            imageProxy.image?.let { process(it, imageProxy) }
        }