Add toggle to invert page color in reader color filter settings (#5713)

(cherry picked from commit 4c8dfd0c0cad40c1412d211cd40355f86152559b)

app/src/main/java/eu/kanade/tachiyomi/data/preference/PreferenceKeys.kt

@@ -55,6 +55,8 @@ object PreferenceKeys {
 
     const val grayscale = "pref_grayscale"
 
+    const val invertedColors = "pref_inverted_colors"
+
     const val defaultReadingMode = "pref_default_reading_mode_key"
 
     const val defaultOrientationType = "pref_default_orientation_type_key"

app/src/main/java/eu/kanade/tachiyomi/data/preference/PreferencesHelper.kt

@@ -133,6 +133,8 @@ class PreferencesHelper(val context: Context) {
 
     fun grayscale() = flowPrefs.getBoolean(Keys.grayscale, false)
 
+    fun invertedColors() = flowPrefs.getBoolean(Keys.invertedColors, false)
+
     fun defaultReadingMode() = prefs.getInt(Keys.defaultReadingMode, ReadingModeType.RIGHT_TO_LEFT.flagValue)
 
     fun defaultOrientationType() = prefs.getInt(Keys.defaultOrientationType, OrientationType.FREE.flagValue)

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

@@ -100,6 +100,7 @@ import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.drop
 import kotlinx.coroutines.flow.launchIn
+import kotlinx.coroutines.flow.merge
 import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.flow.sample
 import kotlinx.coroutines.launch
@@ -1466,12 +1467,26 @@ class ReaderActivity : BaseRxActivity<ReaderActivityBinding, ReaderPresenter>()
      */
     private inner class ReaderConfig {
 
-        private val grayscalePaint by lazy {
-            Paint().apply {
+        private fun getCombinedPaint(grayscale: Boolean, invertedColors: Boolean): Paint {
+            return Paint().apply {
                 colorFilter = ColorMatrixColorFilter(
                     ColorMatrix().apply {
+                        if (grayscale) {
                             setSaturation(0f)
                         }
+                        if (invertedColors) {
+                            postConcat(
+                                ColorMatrix(
+                                    floatArrayOf(
+                                        -1f, 0f, 0f, 0f, 255f,
+                                        0f, -1f, 0f, 0f, 255f,
+                                        0f, 0f, -1f, 0f, 255f,
+                                        0f, 0f, 0f, 1f, 0f
+                                    )
+                                )
+                            )
+                        }
+                    }
                 )
             }
         }
@@ -1523,8 +1538,8 @@ class ReaderActivity : BaseRxActivity<ReaderActivityBinding, ReaderPresenter>()
                 .onEach { setColorFilter(preferences.colorFilter().get()) }
                 .launchIn(lifecycleScope)
 
-            preferences.grayscale().asFlow()
-                .onEach { setGrayscale(it) }
+            merge(preferences.grayscale().asFlow(), preferences.invertedColors().asFlow())
+                .onEach { setLayerPaint(preferences.grayscale().get(), preferences.invertedColors().get()) }
                 .launchIn(lifecycleScope)
 
             preferences.fullscreen().asFlow()
@@ -1675,8 +1690,8 @@ class ReaderActivity : BaseRxActivity<ReaderActivityBinding, ReaderPresenter>()
             binding.colorOverlay.setFilterColor(value, preferences.colorFilterMode().get())
         }
 
-        private fun setGrayscale(enabled: Boolean) {
-            val paint = if (enabled) grayscalePaint else null
+        private fun setLayerPaint(grayscale: Boolean, invertedColors: Boolean) {
+            val paint = if (grayscale || invertedColors) getCombinedPaint(grayscale, invertedColors) else null
             binding.viewerContainer.setLayerType(LAYER_TYPE_HARDWARE, paint)
         }
     }

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

@@ -67,6 +67,7 @@ class ReaderColorFilterSettings @JvmOverloads constructor(context: Context, attr
         binding.customBrightness.bindToPreference(preferences.customBrightness())
         binding.colorFilterMode.bindToPreference(preferences.colorFilterMode())
         binding.grayscale.bindToPreference(preferences.grayscale())
+        binding.invertedColors.bindToPreference(preferences.invertedColors())
 
         binding.seekbarColorFilterAlpha.setOnSeekBarChangeListener(
             object : SimpleSeekBarListener() {

app/src/main/res/layout/reader_color_filter_settings.xml

@@ -193,6 +193,16 @@
             android:textColor="?android:attr/textColorSecondary"
             app:layout_constraintTop_toBottomOf="@id/color_filter_mode" />
 
+        <com.google.android.material.switchmaterial.SwitchMaterial
+            android:id="@+id/inverted_colors"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:paddingStart="16dp"
+            android:paddingEnd="16dp"
+            android:text="@string/pref_inverted_colors"
+            android:textColor="?android:attr/textColorSecondary"
+            app:layout_constraintTop_toBottomOf="@id/grayscale" />
+
         <!-- Brightness -->
 
         <com.google.android.material.switchmaterial.SwitchMaterial
@@ -203,7 +213,7 @@
             android:paddingStart="16dp"
             android:paddingEnd="16dp"
             android:text="@string/pref_custom_brightness"
-            app:layout_constraintTop_toBottomOf="@id/grayscale" />
+            app:layout_constraintTop_toBottomOf="@id/inverted_colors" />
 
         <!-- Brightness value -->
 

app/src/main/res/values/strings.xml

@@ -275,6 +275,7 @@
     <string name="off">Off</string>
     <string name="pref_custom_brightness">Custom brightness</string>
     <string name="pref_grayscale">Grayscale</string>
+    <string name="pref_inverted_colors">Inverted</string>
     <string name="pref_custom_color_filter">Custom color filter</string>
     <string name="pref_color_filter_mode">Color filter blend mode</string>
     <string name="filter_mode_default">Default</string>