Refactor and improve BackgroundImage.getBackgroundImageDimensions()

The method was extracted from BackgroundImage to make it more general as
an extension on Context.

Also switch to using inJustDecodeBounds because we only need the
dimensions so there's no need to load the entire bitmap for this.

Author: lukstbit

AnkiDroid/src/main/java/com/ichi2/anki/DeckPicker.kt

@@ -169,6 +169,7 @@ import com.ichi2.anki.ui.animations.fadeOut
 import com.ichi2.anki.ui.windows.permissions.PermissionsActivity
 import com.ichi2.anki.utils.Destination
 import com.ichi2.anki.utils.ext.dismissAllDialogFragments
+import com.ichi2.anki.utils.ext.getSizeOfBitmapFromCollection
 import com.ichi2.anki.utils.ext.setFragmentResultListener
 import com.ichi2.anki.utils.ext.showDialogFragment
 import com.ichi2.anki.widgets.DeckAdapter
@@ -1084,8 +1085,14 @@ open class DeckPicker :
         // TODO: Temporary fix to stop a crash on startup [15450], it can be removed either:
         // * by moving this check to an upgrade path
         // * once enough time has passed
-        val size = BackgroundImage.getBackgroundImageDimensions(this)
-        if (size.width * size.height * BITMAP_BYTES_PER_PIXEL > BackgroundImage.MAX_BITMAP_SIZE) {
+        // null shouldn't happen as we check for the file being present above this call
+        val (bitmapWidth, bitmapHeight) = getSizeOfBitmapFromCollection(BackgroundImage.FILENAME) ?: return false
+        if (bitmapWidth <= 0 || bitmapHeight <= 0) {
+            Timber.w("Decoding background image for dimensions info failed")
+            deckPickerBinding.background.setBackgroundResource(0)
+            return false
+        }
+        if (bitmapWidth * bitmapHeight * BITMAP_BYTES_PER_PIXEL > BackgroundImage.MAX_BITMAP_SIZE) {
             Timber.w("DeckPicker background image dimensions too large")
             deckPickerBinding.background.setBackgroundResource(0)
             return false

AnkiDroid/src/main/java/com/ichi2/anki/deckpicker/BackgroundImage.kt

@@ -17,7 +17,6 @@
 package com.ichi2.anki.deckpicker
 
 import android.content.Context
-import android.graphics.BitmapFactory
 import android.net.Uri
 import android.provider.MediaStore
 import com.ichi2.anki.CollectionHelper
@@ -105,21 +104,6 @@ object BackgroundImage {
         Prefs.isBackgroundEnabled = true
     }
 
-    data class Size(
-        val width: Int,
-        val height: Int,
-    )
-
-    fun getBackgroundImageDimensions(context: Context): Size {
-        val currentAnkiDroidDirectory = CollectionHelper.getCurrentAnkiDroidDirectory(context)
-        val destFile = File(currentAnkiDroidDirectory, FILENAME)
-        val bmp = BitmapFactory.decodeFile(destFile.absolutePath)
-        val w = bmp.width
-        val h = bmp.height
-        bmp.recycle()
-        return Size(width = w, height = h)
-    }
-
     /**
      * @return `true` if the image no longer exists. `false` if an error occurred
      */

AnkiDroid/src/main/java/com/ichi2/anki/utils/ext/Context.kt

@@ -18,10 +18,14 @@ package com.ichi2.anki.utils.ext
 import android.content.BroadcastReceiver
 import android.content.Context
 import android.content.res.TypedArray
+import android.graphics.Bitmap
+import android.graphics.BitmapFactory
 import android.util.AttributeSet
 import androidx.annotation.AttrRes
 import androidx.annotation.StyleRes
+import com.ichi2.anki.CollectionHelper
 import timber.log.Timber
+import java.io.File
 import kotlin.contracts.ExperimentalContracts
 import kotlin.contracts.InvocationKind
 import kotlin.contracts.contract
@@ -61,3 +65,28 @@ fun Context.unregisterReceiverSilently(receiver: BroadcastReceiver) {
         Timber.d(e, "BroadcastReceiver was not previously registered")
     }
 }
+
+/**
+ * Encapsulates the dimensions of a [Bitmap].
+ * Note: width and height might be set to -1 if there are errors when decoding the file.
+ */
+data class BitmapSize(
+    val width: Int,
+    val height: Int,
+)
+
+/**
+ * Calculate the size of a [Bitmap] from [com.ichi2.anki.libanki.Collection].
+ * @param filename the full name of the [Bitmap] file
+ * @return a [BitmapSize] containing the calculated dimensions or null if the file was not found in
+ * the collection directory
+ */
+fun Context.getSizeOfBitmapFromCollection(filename: String): BitmapSize? {
+    val currentAnkiDroidDirectory = CollectionHelper.getCurrentAnkiDroidDirectory(this)
+    val destFile = File(currentAnkiDroidDirectory, filename)
+    if (!destFile.exists()) return null
+    val opts = BitmapFactory.Options().apply { inJustDecodeBounds = true }
+    // returned bitmap will be null, we just calculate the size
+    BitmapFactory.decodeFile(destFile.absolutePath, opts)
+    return BitmapSize(opts.outWidth, opts.outHeight)
+}