Saving Displayed QR Code as PNG

SaveImage.kt

private fun saveQrImage(
    context: Context,
    qrData: QrData,
    scope: CoroutineScope,
    showSuccessSnackbar: () -> Unit,
    showErrorSnackbar: () -> Unit,
) {

    scope.launch(Dispatchers.IO) {
        val resolver = context.contentResolver
        val fileName = "${qrData.displayName.ifBlank { "qr_code" }}.png"

        val contentValues = ContentValues().apply {
            put(MediaStore.MediaColumns.DISPLAY_NAME, fileName)
            put(MediaStore.MediaColumns.MIME_TYPE, "image/png")
            put(MediaStore.MediaColumns.RELATIVE_PATH, Environment.DIRECTORY_DOWNLOADS)
        }

        val success = try {
            val imageUri = resolver.insert(
                    MediaStore.Downloads.EXTERNAL_CONTENT_URI,
                    contentValues
            ) ?: throw IllegalStateException("Failed to create MediaStore record")

            resolver.openOutputStream(imageUri)
                    ?.use { outputStream ->
                        val qrBitmap = generateQrBitmap(qrData.prettifiedData)
                        qrBitmap.compress(
                                Bitmap.CompressFormat.PNG, 100,
                                outputStream
                        )
                    } ?: throw IllegalStateException("Failed to open output stream")

            true

        } catch (e: Exception) {
            false
        }
        withContext(Dispatchers.IO) {
            if (success) showSuccessSnackbar() else showErrorSnackbar()
        }
    }
}



// uses Zxing

fun generateQrBitmap(
    data: String,
    sizePx: Int = 512,
    marginModules: Int = 2,
    errorCorrection: ErrorCorrectionLevel = ErrorCorrectionLevel.M
): Bitmap {

    val hints = mapOf(
            EncodeHintType.CHARACTER_SET to "UTF-8",
            EncodeHintType.ERROR_CORRECTION to errorCorrection,
            EncodeHintType.MARGIN to marginModules
    )

    val matrix = QRCodeWriter().encode(
            data,
            BarcodeFormat.QR_CODE,
            sizePx,
            sizePx,
            hints
    )

    return createBitmap(sizePx, sizePx)
            .apply {

                for (y in 0 until sizePx) {
                    for (x in 0 until sizePx) {
                       setPixel(x, y, if (matrix[x, y]) 0xFF000000.toInt() else 0xFFFFFFFF.toInt())

                    }
                }
            }
}