1 files changed, 110 insertions, 0 deletions
diff --git a/ui/src/main/java/com/wireguard/android/util/QrCodeFromFileScanner.kt b/ui/src/main/java/com/wireguard/android/util/QrCodeFromFileScanner.kt
new file mode 100644
index 00000000..5d1007e4
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/util/QrCodeFromFileScanner.kt
@@ -0,0 +1,110 @@
+/*
+ * Copyright © 2017-2022 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.util
+
+import android.content.ContentResolver
+import android.graphics.Bitmap
+import android.graphics.BitmapFactory
+import android.net.Uri
+import android.util.Log
+import com.google.zxing.BinaryBitmap
+import com.google.zxing.DecodeHintType
+import com.google.zxing.NotFoundException
+import com.google.zxing.RGBLuminanceSource
+import com.google.zxing.Reader
+import com.google.zxing.Result
+import com.google.zxing.common.HybridBinarizer
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+
+/**
+ * Encapsulates the logic of scanning a barcode from a file,
+ * @property contentResolver - Resolver to read the incoming data
+ * @property reader - An instance of zxing's [Reader] class to parse the image
+ */
+class QrCodeFromFileScanner(
+    private val contentResolver: ContentResolver,
+    private val reader: Reader,
+) {
+
+    private fun scanBitmapForResult(source: Bitmap): Result {
+        val width = source.width
+        val height = source.height
+        val pixels = IntArray(width * height)
+        source.getPixels(pixels, 0, width, 0, 0, width, height)
+
+        val bBitmap = BinaryBitmap(HybridBinarizer(RGBLuminanceSource(width, height, pixels)))
+        return reader.decode(bBitmap, mapOf(DecodeHintType.TRY_HARDER to true))
+    }
+
+    private fun downscaleBitmap(source: Bitmap, scaledSize: Int): Bitmap {
+
+        val originalWidth = source.width
+        val originalHeight = source.height
+
+        var newWidth = -1
+        var newHeight = -1
+        val multFactor: Float
+
+        when {
+            originalHeight > originalWidth -> {
+                newHeight = scaledSize
+                multFactor = originalWidth.toFloat() / originalHeight.toFloat()
+                newWidth = (newHeight * multFactor).toInt()
+            }
+            originalWidth > originalHeight -> {
+                newWidth = scaledSize
+                multFactor = originalHeight.toFloat() / originalWidth.toFloat()
+                newHeight = (newWidth * multFactor).toInt()
+            }
+            originalHeight == originalWidth -> {
+                newHeight = scaledSize
+                newWidth = scaledSize
+            }
+        }
+        return Bitmap.createScaledBitmap(source, newWidth, newHeight, false)
+    }
+
+    private fun doScan(data: Uri): Result {
+        Log.d(TAG, "Starting to scan an image: $data")
+        contentResolver.openInputStream(data).use { inputStream ->
+            val originalBitmap = BitmapFactory.decodeStream(inputStream)
+                ?: throw IllegalArgumentException("Can't decode stream to Bitmap")
+
+            return try {
+                scanBitmapForResult(originalBitmap).also {
+                    Log.d(TAG, "Found result in original image")
+                }
+            } catch (e: Exception) {
+                Log.e(TAG, "Original image scan finished with error: $e, will try downscaled image")
+                val scaleBitmap = downscaleBitmap(originalBitmap, 500)
+                scanBitmapForResult(originalBitmap).also { scaleBitmap.recycle() }
+            } finally {
+                originalBitmap.recycle()
+            }
+        }
+
+    }
+
+    /**
+     * Attempts to parse incoming data
+     * @return result of the decoding operation
+     * @throws NotFoundException when parser didn't find QR code in the image
+     */
+    suspend fun scan(data: Uri) = withContext(Dispatchers.Default) { doScan(data) }
+
+    /**
+     * Given a reference to a file, check if this file could be parsed by this class
+     * @return true if the file can be parsed, false if not
+     */
+    fun validContentType(data: Uri): Boolean {
+        return contentResolver.getType(data)?.startsWith("image/") == true
+    }
+
+    companion object {
+        private const val TAG = "QrCodeFromFileScanner"
+    }
+}