Splitting double pages (#961)

* Split double pages

* various fixes for split double page

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

@@ -74,6 +74,8 @@ object PreferenceKeys {
 
     const val pageLayout = "page_layout"
 
+    const val automaticSplitsPage = "automatic_splits_page"
+
     const val invertDoublePages = "invert_double_pages"
 
     const val readerBottomButtons = "reader_bottom_buttons"

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

@@ -186,6 +186,8 @@ class PreferencesHelper(val context: Context) {
 
     fun pageLayout() = flowPrefs.getInt(Keys.pageLayout, PageLayout.AUTOMATIC.value)
 
+    fun automaticSplitsPage() = flowPrefs.getBoolean(Keys.automaticSplitsPage, false)
+
     fun invertDoublePages() = flowPrefs.getBoolean(Keys.invertDoublePages, false)
 
     fun readerBottomButtons() = flowPrefs.getStringSet(

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

@@ -29,6 +29,7 @@ import androidx.core.view.GestureDetectorCompat
 import androidx.core.view.ViewCompat
 import androidx.core.view.isInvisible
 import androidx.core.view.isVisible
+import androidx.lifecycle.Lifecycle
 import androidx.vectordrawable.graphics.drawable.AnimatedVectorDrawableCompat
 import com.afollestad.materialdialogs.MaterialDialog
 import com.davemorrissey.labs.subscaleview.SubsamplingScaleImageView
@@ -342,8 +343,11 @@ class ReaderActivity :
         binding.chaptersSheet.doublePage.setImageDrawable(
             ContextCompat.getDrawable(
                 this,
-                if (!isDoublePage) R.drawable.ic_single_page_24dp
+                when {
-                else R.drawable.ic_book_open_variant_24dp
+                    isDoublePage -> R.drawable.ic_book_open_variant_24dp
+                    (viewer as? PagerViewer)?.config?.splitPages == true -> R.drawable.ic_book_open_split_24dp
+                    else -> R.drawable.ic_single_page_24dp
+                }
             )
         )
         with(binding.readerNav) {
@@ -354,11 +358,6 @@ class ReaderActivity :
                 }
             }
         }
-        binding.chaptersSheet.doublePage.compatToolTipText =
-            getString(
-                if (isDoublePage) R.string.switch_to_single
-                else R.string.switch_to_double
-            )
     }
 
     private fun updateOrientationShortcut(preference: Int) {
@@ -554,14 +553,39 @@ class ReaderActivity :
         }
 
         with(binding.chaptersSheet) {
-            doublePage.setOnClickListener {
+            with(doublePage) {
+                compatToolTipText = getString(R.string.page_layout)
+                setOnClickListener {
+                    val config = (viewer as? PagerViewer)?.config
+                    val selectedId = when {
+                        config?.doublePages == true -> PageLayout.DOUBLE_PAGES
+                        config?.splitPages == true -> PageLayout.SPLIT_PAGES
+                        else -> PageLayout.SINGLE_PAGE
+                    }
+                    popupMenu(
+                        items = listOf(
+                            PageLayout.SINGLE_PAGE,
+                            PageLayout.DOUBLE_PAGES,
+                            PageLayout.SPLIT_PAGES,
+                        ).map { it.value to it.stringRes },
+                        selectedItemId = selectedId.value,
+                    ) {
+                        val newLayout = PageLayout.fromPreference(itemId)
+
                         if (preferences.pageLayout().get() == PageLayout.AUTOMATIC.value) {
                             (viewer as? PagerViewer)?.config?.let { config ->
-                        config.doublePages = !config.doublePages
+                                config.doublePages = newLayout == PageLayout.DOUBLE_PAGES
+                                if (newLayout == PageLayout.SINGLE_PAGE) {
+                                    preferences.automaticSplitsPage().set(false)
+                                } else if (newLayout == PageLayout.SPLIT_PAGES) {
+                                    preferences.automaticSplitsPage().set(true)
+                                }
                                 reloadChapters(config.doublePages, true)
                             }
                         } else {
-                    preferences.pageLayout().set(1 - preferences.pageLayout().get())
+                            preferences.pageLayout().set(newLayout.value)
+                        }
+                    }
                 }
             }
             cropBordersSheetButton.setOnClickListener {
@@ -917,6 +941,9 @@ class ReaderActivity :
             setDoublePageMode(pViewer)
         } else {
             pViewer.config.doublePages = doublePages
+            if (pViewer.config.autoDoublePages) {
+                pViewer.config.splitPages = preferences.automaticSplitsPage().get() && !pViewer.config.doublePages
+            }
         }
         val currentChapter = presenter.getCurrentChapter()
         if (doublePages) {
@@ -925,7 +952,7 @@ class ReaderActivity :
                 binding.readerNav.pageSeekbar.progress +
                     (
                         currentChapter?.pages?.take(binding.readerNav.pageSeekbar.progress)
-                            ?.count { it.fullPage || it.isolatedPage } ?: 0
+                            ?.count { it.fullPage == true || it.isolatedPage } ?: 0
                         )
                 ) % 2 != 0
         }
@@ -953,7 +980,7 @@ class ReaderActivity :
                 currentChapter.requestedPage +
                     (
                         currentChapter.pages?.take(currentChapter.requestedPage)
-                            ?.count { it.fullPage || it.isolatedPage } ?: 0
+                            ?.count { it.fullPage == true || it.isolatedPage } ?: 0
                         )
                 ) % 2 != 0
         }
@@ -1042,7 +1069,7 @@ class ReaderActivity :
         val currentPage = if (hasExtraPage) {
             if (resources.isLTR) "${page.number}-${page.number + 1}" else "${page.number + 1}-${page.number}"
         } else {
-            "${page.number}"
+            "${page.number}${if (page.firstHalf == false) "*" else ""}"
         }
 
         val totalPages = pages.size.toString()
@@ -1347,6 +1374,9 @@ class ReaderActivity :
     private fun setDoublePageMode(viewer: PagerViewer) {
         val currentOrientation = resources.configuration.orientation
         viewer.config.doublePages = (currentOrientation == Configuration.ORIENTATION_LANDSCAPE)
+        if (viewer.config.autoDoublePages) {
+            viewer.config.splitPages = preferences.automaticSplitsPage().get() && !viewer.config.doublePages
+        }
     }
 
     private fun handleIntentAction(intent: Intent): Boolean {
@@ -1438,6 +1468,18 @@ class ReaderActivity :
 
             preferences.pageLayout().asImmediateFlowIn(scope) { setBottomNavButtons(it) }
 
+            preferences.automaticSplitsPage().asFlow()
+                .drop(1)
+                .onEach {
+                    val isPaused = !this@ReaderActivity.lifecycle.currentState.isAtLeast(Lifecycle.State.RESUMED)
+                    if (isPaused) {
+                        (viewer as? PagerViewer)?.config?.let { config ->
+                            reloadChapters(config.doublePages, true)
+                        }
+                    }
+                }
+                .launchIn(scope)
+
             preferences.readerBottomButtons().asImmediateFlowIn(scope) { updateBottomShortcuts() }
 
             preferences.readWithTapping().asImmediateFlowIn(scope) {

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

@@ -490,7 +490,7 @@ class ReaderPresenter(
         if (shouldTrack &&
             // For double pages, check if the second to last page is doubled up
             (
-                selectedChapter.pages?.lastIndex == page.index ||
+                (selectedChapter.pages?.lastIndex == page.index && page.firstHalf != true) ||
                     (hasExtraPage && selectedChapter.pages?.lastIndex?.minus(1) == page.index)
                 )
         ) {

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

@@ -0,0 +1,16 @@
+package eu.kanade.tachiyomi.ui.reader.model
+
+class InsertPage(parent: ReaderPage) : ReaderPage(
+    parent.index,
+    parent.url,
+    parent.imageUrl
+) {
+
+    override var chapter: ReaderChapter = parent.chapter
+
+    init {
+        fullPage = true
+        firstHalf = false
+        stream = parent.stream
+    }
+}

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

@@ -4,7 +4,7 @@ import android.graphics.drawable.Drawable
 import eu.kanade.tachiyomi.source.model.Page
 import java.io.InputStream
 
-class ReaderPage(
+open class ReaderPage(
     index: Int,
     url: String = "",
     imageUrl: String? = null,
@@ -14,15 +14,21 @@ class ReaderPage(
     /** Value to check if this page is used to as if it was too wide */
     var shiftedPage: Boolean = false,
     /** Value to check if a page is can be doubled up, but can't because the next page is too wide */
-    var isolatedPage: Boolean = false
+    var isolatedPage: Boolean = false,
+    var firstHalf: Boolean? = null,
+    var longPage: Boolean? = null
 ) : Page(index, url, imageUrl, null) {
 
-    lateinit var chapter: ReaderChapter
+    open lateinit var chapter: ReaderChapter
 
     /** Value to check if a page is too wide to be doubled up */
-    var fullPage: Boolean = false
+    var fullPage: Boolean? = null
         set(value) {
             field = value
-            if (value) shiftedPage = false
+            longPage = value
+            if (value == true) shiftedPage = false
         }
+
+    fun isFromSamePage(page: ReaderPage): Boolean =
+        index == page.index && chapter.chapter.id == page.chapter.chapter.id
 }

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

@@ -7,6 +7,7 @@ enum class PageLayout(val value: Int, @StringRes val stringRes: Int, @StringRes
     SINGLE_PAGE(0, R.string.single_page),
     DOUBLE_PAGES(1, R.string.double_pages),
     AUTOMATIC(2, R.string.automatic, R.string.automatic_orientation),
+    SPLIT_PAGES(3, R.string.split_double_pages)
     ;
 
     @StringRes val fullStringRes = _fullStringRes ?: stringRes

app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/PagerConfig.kt

@@ -58,6 +58,9 @@ class PagerConfig(
 
     var autoDoublePages = preferences.pageLayout().get() == PageLayout.AUTOMATIC.value
 
+    var splitPages = preferences.pageLayout().get() == PageLayout.SPLIT_PAGES.value
+    var autoSplitPages = preferences.automaticSplitsPage().get()
+
     init {
         preferences.pageTransitions()
             .register({ usePageTransitions = it })
@@ -103,6 +106,7 @@ class PagerConfig(
             .drop(1)
             .onEach {
                 autoDoublePages = it == PageLayout.AUTOMATIC.value
+                splitPages = it == PageLayout.SPLIT_PAGES.value
                 if (!autoDoublePages) {
                     doublePages = it == PageLayout.DOUBLE_PAGES.value
                 }
@@ -114,9 +118,12 @@ class PagerConfig(
                 autoDoublePages = it == PageLayout.AUTOMATIC.value
                 if (!autoDoublePages) {
                     doublePages = it == PageLayout.DOUBLE_PAGES.value
+                    splitPages = it == PageLayout.SPLIT_PAGES.value
                 }
             })
 
+        preferences.automaticSplitsPage()
+            .register({ autoSplitPages = it })
         navigationOverlayForNewUser = preferences.showNavigationOverlayNewUser().get()
         if (navigationOverlayForNewUser) {
             preferences.showNavigationOverlayNewUser().set(false)

app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/PagerPageHolder.kt

@@ -348,7 +348,7 @@ class PagerPageHolder(
                 val stream = streamFn().buffered(16)
 
                 val stream2 = if (extraPage != null) streamFn2?.invoke()?.buffered(16) else null
-                openStream = this@PagerPageHolder.mergePages(stream, stream2)
+                openStream = this@PagerPageHolder.mergeOrSplitPages(stream, stream2)
                 ImageUtil.isAnimatedAndSupported(stream) ||
                     if (stream2 != null) ImageUtil.isAnimatedAndSupported(stream2) else false
             }
@@ -507,6 +507,15 @@ class PagerPageHolder(
             }
             setOnImageEventListener(
                 object : SubsamplingScaleImageView.DefaultOnImageEventListener() {
+
+                    override fun onImageLoaded() {
+                        if (this@PagerPageHolder.extraPage == null &&
+                            this@PagerPageHolder.page.longPage == null &&
+                            sHeight < sWidth
+                        ) {
+                            this@PagerPageHolder.page.longPage = true
+                        }
+                    }
                     override fun onReady() {
                         var centerV = 0f
                         when (config.imageZoomType) {
@@ -651,9 +660,63 @@ class PagerPageHolder(
         return decodeLayout
     }
 
-    private fun mergePages(imageStream: InputStream, imageStream2: InputStream?): InputStream {
+    private fun mergeOrSplitPages(imageStream: InputStream, imageStream2: InputStream?): InputStream {
-        imageStream2 ?: return imageStream
+        if (page.longPage == true && viewer.config.splitPages) {
-        if (page.fullPage) return imageStream
+            val imageBytes = imageStream.readBytes()
+            val imageBitmap = try {
+                BitmapFactory.decodeByteArray(imageBytes, 0, imageBytes.size)
+            } catch (e: Exception) {
+                imageStream.close()
+                Timber.e("Cannot split page ${e.message}")
+                return imageBytes.inputStream()
+            }
+            val isLTR = (viewer !is R2LPagerViewer).xor(viewer.config.invertDoublePages)
+            return ImageUtil.splitBitmap(imageBitmap, (page.firstHalf == false).xor(!isLTR)) {
+                scope?.launchUI {
+                    if (it == 100) {
+                        progressBar.completeAndFadeOut()
+                    } else {
+                        progressBar.setProgress(it)
+                    }
+                }
+            }
+        }
+        if (imageStream2 == null) {
+            if (viewer.config.splitPages && page.longPage == null) {
+                val imageBytes = imageStream.readBytes()
+                val imageBitmap = try {
+                    BitmapFactory.decodeByteArray(imageBytes, 0, imageBytes.size)
+                } catch (e: Exception) {
+                    imageStream.close()
+                    page.longPage = true
+                    skipExtra = true
+                    Timber.e("Cannot split page ${e.message}")
+                    return imageBytes.inputStream()
+                }
+                val height = imageBitmap.height
+                val width = imageBitmap.width
+                return if (height < width) {
+                    imageStream.close()
+                    page.longPage = true
+                    skipExtra = true
+                    val isLTR = (viewer !is R2LPagerViewer).xor(viewer.config.invertDoublePages)
+                    return ImageUtil.splitBitmap(imageBitmap, !isLTR) {
+                        scope?.launchUI {
+                            if (it == 100) {
+                                progressBar.completeAndFadeOut()
+                            } else {
+                                progressBar.setProgress(it)
+                            }
+                        }
+                    }
+                } else {
+                    page.longPage = false
+                    imageBytes.inputStream()
+                }
+            }
+            return imageStream
+        }
+        if (page.fullPage == true) return imageStream
         if (ImageUtil.isAnimatedAndSupported(imageStream)) {
             page.fullPage = true
             skipExtra = true
@@ -732,7 +795,7 @@ class PagerPageHolder(
     }
 
     private fun splitDoublePages() {
-        extraPage ?: return
+        // extraPage ?: return
         viewer.splitDoublePages(page)
         if (extraPage?.fullPage == true) {
             extraPage = null

app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/PagerViewer.kt

@@ -156,7 +156,11 @@ abstract class PagerViewer(val activity: ReaderActivity) : BaseViewer {
             val allowPreload = checkAllowPreload(page.first as? ReaderPage)
             currentPage = page.first
             when (val aPage = page.first) {
-                is ReaderPage -> onReaderPageSelected(aPage, allowPreload, page.second != null)
+                is ReaderPage -> onReaderPageSelected(
+                    aPage,
+                    allowPreload,
+                    page.second is ReaderPage
+                )
                 is ChapterTransition -> onTransitionSelected(aPage)
             }
         }
@@ -275,7 +279,14 @@ abstract class PagerViewer(val activity: ReaderActivity) : BaseViewer {
      */
     override fun moveToPage(page: ReaderPage, animated: Boolean) {
         Timber.d("moveToPage ${page.number}")
-        val position = adapter.joinedItems.indexOfFirst { it.first == page || it.second == page }
+        val position = adapter.joinedItems.indexOfFirst {
+            it.first == page || it.second == page ||
+                (
+                    config.splitPages && it.first is ReaderPage &&
+                        (it.first as? ReaderPage)?.isFromSamePage(page) == true &&
+                        (it.first as? ReaderPage)?.firstHalf != false
+                    )
+        }
         if (position != -1) {
             val currentPosition = pager.currentItem
             pager.setCurrentItem(position, animated)
@@ -288,7 +299,7 @@ abstract class PagerViewer(val activity: ReaderActivity) : BaseViewer {
                 val joinedItem = adapter.joinedItems.firstOrNull { it.first == page || it.second == page }
                 activity.onPageSelected(
                     joinedItem?.first as? ReaderPage ?: page,
-                    joinedItem?.second != null
+                    joinedItem?.second is ReaderPage
                 )
             }
         } else {

app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/PagerViewerAdapter.kt

@@ -3,6 +3,7 @@ package eu.kanade.tachiyomi.ui.reader.viewer.pager
 import android.view.View
 import android.view.ViewGroup
 import eu.kanade.tachiyomi.ui.reader.model.ChapterTransition
+import eu.kanade.tachiyomi.ui.reader.model.InsertPage
 import eu.kanade.tachiyomi.ui.reader.model.ReaderChapter
 import eu.kanade.tachiyomi.ui.reader.model.ReaderPage
 import eu.kanade.tachiyomi.ui.reader.model.ViewerChapters
@@ -55,7 +56,7 @@ class PagerViewerAdapter(private val viewer: PagerViewer) : ViewPagerAdapter() {
             // however we should take account full pages when deciding
             val numberOfFullPages =
                 (
-                    chapters.prevChapter.pages?.count { it.fullPage || it.isolatedPage }
+                    chapters.prevChapter.pages?.count { it.fullPage == true || it.isolatedPage }
                         ?: 0
                     )
             if (prevPages != null) {
@@ -134,7 +135,8 @@ class PagerViewerAdapter(private val viewer: PagerViewer) : ViewPagerAdapter() {
     override fun getItemPosition(view: Any): Int {
         if (view is PositionableView) {
             val position = joinedItems.indexOfFirst {
-                view.item == (it.first to it.second)
+                val secondPage = it.second as? ReaderPage
+                view.item == it.first to secondPage
             }
             if (position != -1) {
                 return position
@@ -148,6 +150,9 @@ class PagerViewerAdapter(private val viewer: PagerViewer) : ViewPagerAdapter() {
     fun splitDoublePages(current: ReaderPage) {
         val oldCurrent = joinedItems.getOrNull(viewer.pager.currentItem)
         setJoinedItems(
+            if (viewer.config.splitPages) {
+                (oldCurrent?.first as? ReaderPage)?.firstHalf == false
+            } else {
                 oldCurrent?.second == current ||
                     (current.index + 1) < (
                     (
@@ -155,6 +160,7 @@ class PagerViewerAdapter(private val viewer: PagerViewer) : ViewPagerAdapter() {
                             ?: oldCurrent?.first
                         ) as? ReaderPage
                     )?.index ?: 0
+            }
         )
 
         // The listener may be removed when we split a page, so the ui may not have updated properly
@@ -170,8 +176,36 @@ class PagerViewerAdapter(private val viewer: PagerViewer) : ViewPagerAdapter() {
             // If not in double mode, set up items like before
             subItems.forEach {
                 (it as? ReaderPage)?.shiftedPage = false
+                (it as? ReaderPage)?.firstHalf = null
             }
+            if (viewer.config.splitPages) {
+                var itemIndex = 0
+                val pagedItems = subItems.toMutableList()
+                while (itemIndex < pagedItems.size) {
+                    val page = pagedItems[itemIndex] as? ReaderPage
+                    if (page == null) {
+                        itemIndex++
+                        continue
+                    }
+                    if (page.longPage == true) {
+                        page.firstHalf = true
+                        // Add a second halved page after each full page.
+                        pagedItems[itemIndex] = InsertPage(page).apply { firstHalf = true }
+                        val secondHalf = InsertPage(page)
+                        pagedItems.add(itemIndex + 1, secondHalf)
+                        itemIndex++
+                    }
+                    itemIndex++
+                }
+                this.joinedItems = pagedItems.map {
+                    Pair<Any, Any?>(
+                        it,
+                        if ((it as? ReaderPage)?.fullPage == true) (it as? ReaderPage)?.firstHalf else null
+                    )
+                }.toMutableList()
+            } else {
                 this.joinedItems = subItems.map { Pair<Any, Any?>(it, null) }.toMutableList()
+            }
             if (viewer is R2LPagerViewer) {
                 joinedItems.reverse()
             }
@@ -200,6 +234,7 @@ class PagerViewerAdapter(private val viewer: PagerViewer) : ViewPagerAdapter() {
 
                 items.forEach {
                     it?.shiftedPage = false
+                    it?.firstHalf = null
                 }
                 // Step 3: If pages have been shifted,
                 if (viewer.config.shiftDoublePage) {
@@ -221,7 +256,7 @@ class PagerViewerAdapter(private val viewer: PagerViewer) : ViewPagerAdapter() {
                         )
                         // Add a shifted page to the first place there isnt a full page
                         (fullPageBeforeIndex until items.size).forEach {
-                            if (items[it]?.fullPage == false) {
+                            if (items[it]?.fullPage != true) {
                                 items[it]?.shiftedPage = true
                                 return@loop
                             }
@@ -281,10 +316,23 @@ class PagerViewerAdapter(private val viewer: PagerViewer) : ViewPagerAdapter() {
             when {
                 (oldCurrent?.first as? ReaderPage)?.chapter != currentChapter &&
                     (oldCurrent?.first as? ChapterTransition)?.from != currentChapter -> subItems.find { (it as? ReaderPage)?.chapter == currentChapter }
-                useSecondPage -> (oldCurrent?.second ?: oldCurrent?.first)
+                useSecondPage && oldCurrent?.second is ReaderPage -> (oldCurrent.second ?: oldCurrent.first)
                 else -> oldCurrent?.first ?: return
             }
-        var index = joinedItems.indexOfFirst { it.first == newPage || it.second == newPage }
+        var index = joinedItems.indexOfFirst {
+            val readerPage = it.first as? ReaderPage
+            val readerPage2 = it.second as? ReaderPage
+            val newReaderPage = newPage as? ReaderPage
+            it.first == newPage || it.second == newPage ||
+                (
+                    readerPage != null && newReaderPage != null &&
+                        (
+                            readerPage.isFromSamePage(newReaderPage) ||
+                                readerPage2?.isFromSamePage(newReaderPage) == true
+                            ) &&
+                        (readerPage.firstHalf == !useSecondPage || readerPage.firstHalf == null)
+                    )
+        }
         if (newPage is ChapterTransition && index == -1 && !forceTransition) {
             val newerPage = if (newPage is ChapterTransition.Next) {
                 joinedItems.filter {
@@ -297,6 +345,8 @@ class PagerViewerAdapter(private val viewer: PagerViewer) : ViewPagerAdapter() {
             }
             index = joinedItems.indexOfFirst { it.first == newerPage || it.second == newerPage }
         }
+        if (index > -1) {
             viewer.pager.setCurrentItem(index, false)
         }
+    }
 }

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

@@ -255,6 +255,12 @@ class SettingsReaderController : SettingsController() {
             infoPreference(R.string.automatic_can_still_switch).apply {
                 preferences.pageLayout().asImmediateFlowIn(viewScope) { isVisible = it == PageLayout.AUTOMATIC.value }
             }
+            switchPreference {
+                key = Keys.automaticSplitsPage
+                titleRes = R.string.split_double_pages_portrait
+                defaultValue = false
+                preferences.pageLayout().asImmediateFlowIn(viewScope) { isVisible = it == PageLayout.AUTOMATIC.value }
+            }
             switchPreference {
                 key = Keys.invertDoublePages
                 titleRes = R.string.invert_double_pages

app/src/main/java/eu/kanade/tachiyomi/util/system/ImageUtil.kt

@@ -278,6 +278,24 @@ object ImageUtil {
         return ColorDrawable(backgroundColor)
     }
 
+    fun splitBitmap(
+        imageBitmap: Bitmap,
+        secondHalf: Boolean,
+        progressCallback: ((Int) -> Unit)? = null
+    ): ByteArrayInputStream {
+        val height = imageBitmap.height
+        val width = imageBitmap.width
+        val result = Bitmap.createBitmap(width / 2, height, Bitmap.Config.ARGB_8888)
+        val canvas = Canvas(result)
+        progressCallback?.invoke(98)
+        canvas.drawBitmap(imageBitmap, Rect(if (!secondHalf) 0 else width / 2, 0, if (secondHalf) width else width / 2, height), result.rect, null)
+        progressCallback?.invoke(99)
+        val output = ByteArrayOutputStream()
+        result.compress(Bitmap.CompressFormat.JPEG, 100, output)
+        progressCallback?.invoke(100)
+        return ByteArrayInputStream(output.toByteArray())
+    }
+
     fun mergeBitmaps(
         imageBitmap: Bitmap,
         imageBitmap2: Bitmap,

app/src/main/res/drawable/ic_book_open_split_24dp.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+  <path
+      android:fillColor="#FF000000"
+      android:pathData="M13.9,12h6.5v1.4h-6.5M13.9,9.7h6.5v1.4h-6.5M13.9,14.4h6.5v1.4h-6.5M21.3,4.6H13l0.6,1L13,6.5v12.1l0.6,0.9L13,20.4h8.4c1,0 1.9,-0.8 1.9,-1.9V6.5C23.2,5.4 22.3,4.6 21.3,4.6M21.3,18.5H13V6.5h8.4M7.3,4.6H3c-1,0 -1.9,0.8 -1.9,1.9v12.1c0,1 0.8,1.9 1.9,1.9h8.4l-1.1,-1.9l1.1,-2.2l-1,-1.8l1,-2l-0.9,-2.2l0.9,-1.8l-0.9,-2l0.9,-1.9"/>
+</vector>

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

@@ -113,6 +113,7 @@
         <item>@string/single_page</item>
         <item>@string/double_pages</item>
         <item>@string/automatic</item>
+        <item>@string/split_double_pages</item>
     </string-array>
 
     <string-array name="invert_tapping_mode">

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

@@ -382,6 +382,7 @@
     <string name="reduces_banding_impacts_performance">Reduces banding, but impacts
         performance</string>
     <string name="invert_double_pages">Invert double pages</string>
+    <string name="split_double_pages_portrait">Split double pages in portrait</string>
     <string name="crop_borders">Crop borders</string>
     <string name="crop_borders_paged">Crop borders (Paged)</string>
     <string name="crop_borders_webtoon">Crop borders (Webtoon)</string>
@@ -421,6 +422,7 @@
     <string name="original_size">Original size</string>
     <string name="smart_fit">Smart fit</string>
     <string name="zoom_start_position">Zoom start position</string>
+    <string name="split_double_pages">Split double pages</string>
     <string name="double_pages">Double pages</string>
     <string name="single_page">Single page</string>
     <string name="switch_to_double">Switch to double pages</string>