Reader grayscale filter (closes #2822)

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

@@ -49,6 +49,8 @@ object PreferenceKeys {
 
     const val colorFilterMode = "color_filter_mode"
 
+    const val grayscale = "pref_grayscale"
+
     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

@@ -121,6 +121,8 @@ class PreferencesHelper(val context: Context) {
 
     fun colorFilterMode() = flowPrefs.getInt(Keys.colorFilterMode, 0)
 
+    fun grayscale() = flowPrefs.getBoolean(Keys.grayscale, 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

@@ -8,12 +8,16 @@ import android.content.Context
 import android.content.Intent
 import android.graphics.Bitmap
 import android.graphics.Color
+import android.graphics.ColorMatrix
+import android.graphics.ColorMatrixColorFilter
+import android.graphics.Paint
 import android.os.Build
 import android.os.Bundle
 import android.view.KeyEvent
 import android.view.Menu
 import android.view.MenuItem
 import android.view.MotionEvent
+import android.view.View.LAYER_TYPE_HARDWARE
 import android.view.WindowManager
 import android.view.animation.Animation
 import android.view.animation.AnimationUtils
@@ -789,6 +793,16 @@ class ReaderActivity : BaseRxActivity<ReaderActivityBinding, ReaderPresenter>()
      */
     private inner class ReaderConfig {
 
+        private val grayscalePaint by lazy {
+            Paint().apply {
+                colorFilter = ColorMatrixColorFilter(
+                    ColorMatrix().apply {
+                        setSaturation(0f)
+                    }
+                )
+            }
+        }
+
         /**
          * Initializes the reader subscriptions.
          */
@@ -827,6 +841,10 @@ class ReaderActivity : BaseRxActivity<ReaderActivityBinding, ReaderPresenter>()
             preferences.colorFilterMode().asFlow()
                 .onEach { setColorFilter(preferences.colorFilter().get()) }
                 .launchIn(lifecycleScope)
+
+            preferences.grayscale().asFlow()
+                .onEach { setGrayscale(it) }
+                .launchIn(lifecycleScope)
         }
 
         /**
@@ -934,5 +952,10 @@ class ReaderActivity : BaseRxActivity<ReaderActivityBinding, ReaderPresenter>()
             binding.colorOverlay.isVisible = true
             binding.colorOverlay.setFilterColor(value, preferences.colorFilterMode().get())
         }
+
+        private fun setGrayscale(enabled: Boolean) {
+            val paint = if (enabled) grayscalePaint else null
+            binding.viewerContainer.setLayerType(LAYER_TYPE_HARDWARE, paint)
+        }
     }
 }

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

@@ -14,7 +14,7 @@ import androidx.lifecycle.lifecycleScope
 import eu.kanade.tachiyomi.data.preference.PreferencesHelper
 import eu.kanade.tachiyomi.databinding.ReaderColorFilterSettingsBinding
 import eu.kanade.tachiyomi.ui.reader.ReaderActivity
-import eu.kanade.tachiyomi.widget.IgnoreFirstSpinnerListener
+import eu.kanade.tachiyomi.util.preference.bindToPreference
 import eu.kanade.tachiyomi.widget.SimpleSeekBarListener
 import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.onEach
@@ -63,20 +63,10 @@ class ReaderColorFilterSettings @JvmOverloads constructor(context: Context, attr
         binding.seekbarColorFilterBlue.progress = argb[3]
 
         // Set listeners
-        binding.switchColorFilter.isChecked = preferences.colorFilter().get()
-        binding.switchColorFilter.setOnCheckedChangeListener { _, isChecked ->
-            preferences.colorFilter().set(isChecked)
-        }
-
-        binding.customBrightness.isChecked = preferences.customBrightness().get()
-        binding.customBrightness.setOnCheckedChangeListener { _, isChecked ->
-            preferences.customBrightness().set(isChecked)
-        }
-
-        binding.colorFilterMode.onItemSelectedListener = IgnoreFirstSpinnerListener { position ->
-            preferences.colorFilterMode().set(position)
-        }
-        binding.colorFilterMode.setSelection(preferences.colorFilterMode().get(), false)
+        binding.switchColorFilter.bindToPreference(preferences.colorFilter())
+        binding.customBrightness.bindToPreference(preferences.customBrightness())
+        binding.colorFilterMode.bindToPreference(preferences.colorFilterMode())
+        binding.grayscale.bindToPreference(preferences.grayscale())
 
         binding.seekbarColorFilterAlpha.setOnSeekBarChangeListener(
             object : SimpleSeekBarListener() {