Custom color filter for reader (#434)

* [WIP] Custom color filter for reader

* Improvements

* temp image to prevent build error

* Shift all the bits

* Some improvements. Removed DiscreteSeekBar

* Improvements

* API 16 + fixes

* Reduced lag. Fixed brightness value being reset to 0

* Small fixes

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

@@ -26,6 +26,10 @@ class PreferenceKeys(context: Context) {
 
     val customBrightnessValue = context.getString(R.string.pref_custom_brightness_value_key)
 
+    val colorFilter = context.getString(R.string.pref_color_filter_key)
+
+    val colorFilterValue = context.getString(R.string.pref_color_filter_value_key)
+
     val defaultViewer = context.getString(R.string.pref_default_viewer_key)
 
     val imageScaleType = context.getString(R.string.pref_image_scale_type_key)

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

@@ -52,6 +52,10 @@ class PreferencesHelper(context: Context) {
 
     fun customBrightnessValue() = rxPrefs.getInteger(keys.customBrightnessValue, 0)
 
+    fun colorFilter() = rxPrefs.getBoolean(keys.colorFilter, false)
+
+    fun colorFilterValue() = rxPrefs.getInteger(keys.colorFilterValue, 0)
+
     fun defaultViewer() = prefs.getInt(keys.defaultViewer, 1)
 
     fun imageScaleType() = rxPrefs.getInteger(keys.imageScaleType, 1)