preload just 1 fullscreen image per side, with more dynamic resolution

app/src/main/kotlin/com/simplemobiletools/gallery/activities/ViewPagerActivity.kt

@@ -54,6 +54,7 @@ class ViewPagerActivity : SimpleActivity(), ViewPager.OnPageChangeListener, View
     companion object {
         var screenWidth = 0
         var screenHeight = 0
+        var screenDensity = 0f
     }
 
     override fun onCreate(savedInstanceState: Bundle?) {
@@ -174,13 +175,13 @@ class ViewPagerActivity : SimpleActivity(), ViewPager.OnPageChangeListener, View
         windowManager.defaultDisplay.getMetrics(metrics)
         screenWidth = metrics.widthPixels
         screenHeight = metrics.heightPixels
+        screenDensity = metrics.density
     }
 
     private fun updatePagerItems() {
         val pagerAdapter = MyPagerAdapter(this, supportFragmentManager, mMedia)
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1 && !isDestroyed) {
             view_pager?.apply {
-                offscreenPageLimit = 2
                 adapter = pagerAdapter
                 currentItem = mPos
                 addOnPageChangeListener(this@ViewPagerActivity)

app/src/main/kotlin/com/simplemobiletools/gallery/fragments/PhotoFragment.kt

@@ -134,9 +134,10 @@ class PhotoFragment : ViewPagerFragment() {
     }
 
     private fun loadBitmap(degrees: Float = 0f) {
+        val densiy = ViewPagerActivity.screenDensity
         Picasso.with(activity)
                 .load("file:${medium.path}")
-                .resize(ViewPagerActivity.screenWidth * 2, ViewPagerActivity.screenHeight * 2)
+                .resize((ViewPagerActivity.screenWidth * densiy).toInt(), (ViewPagerActivity.screenHeight * densiy).toInt())
                 .priority(if (isFragmentVisible) Picasso.Priority.HIGH else Picasso.Priority.LOW)
                 .rotate(degrees)
                 .centerInside()