Add 32-bit color mode to reader settings (#1941)

* add ARGB_8888 mode to reader settings

* Only show option on Oreo or later.
Only show option in settings screen.

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderActivity.kt

@@ -6,6 +6,7 @@ import android.content.Context
 import android.content.Intent
 import android.content.pm.ActivityInfo
 import android.content.res.Configuration
+import android.graphics.Bitmap
 import android.graphics.Color
 import android.os.Build
 import android.os.Bundle
@@ -13,6 +14,7 @@ import android.view.*
 import android.view.animation.Animation
 import android.view.animation.AnimationUtils
 import android.widget.SeekBar
+import com.davemorrissey.labs.subscaleview.SubsamplingScaleImageView
 import eu.kanade.tachiyomi.R
 import eu.kanade.tachiyomi.data.database.models.Chapter
 import eu.kanade.tachiyomi.data.database.models.Manga
@@ -558,6 +560,9 @@ class ReaderActivity : BaseRxActivity<ReaderPresenter>() {
             subscriptions += preferences.showPageNumber().asObservable()
                 .subscribe { setPageNumberVisibility(it) }
 
+            subscriptions += preferences.trueColor().asObservable()
+                .subscribe { setTrueColor(it) }
+
             subscriptions += preferences.fullscreen().asObservable()
                 .subscribe { setFullscreen(it) }
 
@@ -614,6 +619,16 @@ class ReaderActivity : BaseRxActivity<ReaderPresenter>() {
             page_number.visibility = if (visible) View.VISIBLE else View.INVISIBLE
         }
 
+        /**
+         * Sets the 32-bit color mode according to [enabled].
+         */
+        private fun setTrueColor(enabled: Boolean) {
+            if (enabled)
+                SubsamplingScaleImageView.setPreferredBitmapConfig(Bitmap.Config.ARGB_8888)
+            else
+                SubsamplingScaleImageView.setPreferredBitmapConfig(Bitmap.Config.RGB_565)
+        }
+
         /**
          * Sets the fullscreen reading mode (immersive) according to [enabled].
          */