Fix reader transition color scheme in auto background mode (#1487)

(cherry picked from commit 36d5ee0763be2b0bcc65f9d061961d86359fe6f6)

app/src/main/java/eu/kanade/tachiyomi/util/system/ContextExtensions.kt

@@ -16,6 +16,7 @@ import androidx.core.content.getSystemService
 import androidx.core.net.toUri
 import com.hippo.unifile.UniFile
 import eu.kanade.domain.ui.UiPreferences
+import eu.kanade.domain.ui.model.ThemeMode
 import eu.kanade.tachiyomi.BuildConfig
 import eu.kanade.tachiyomi.R
 import eu.kanade.tachiyomi.ui.base.delegate.ThemingDelegate
@@ -119,9 +120,13 @@ fun Context.createFileInCacheDir(name: String): File {
 fun Context.createReaderThemeContext(): Context {
     val preferences = Injekt.get<UiPreferences>()
     val readerPreferences = Injekt.get<ReaderPreferences>()
+    val themeMode = preferences.themeMode().get()
     val isDarkBackground = when (readerPreferences.readerTheme().get()) {
         1, 2 -> true // Black, Gray
-        3 -> applicationContext.isNightMode() // Automatic bg uses activity background by default
+        3 -> when (themeMode) { // Automatic bg uses activity background by default
+            ThemeMode.SYSTEM -> applicationContext.isNightMode()
+            else -> themeMode == ThemeMode.DARK
+        }
         else -> false // White
     }
     val expected = if (isDarkBackground) Configuration.UI_MODE_NIGHT_YES else Configuration.UI_MODE_NIGHT_NO