Implement simple pages copping

app/src/main/java/org/koitharu/kotatsu/domain/MangaUtils.kt

@@ -1,7 +1,11 @@
 package org.koitharu.kotatsu.domain
 
+import android.graphics.Bitmap
 import android.graphics.BitmapFactory
+import android.graphics.Color
+import android.graphics.Rect
 import android.util.Size
+import androidx.core.graphics.get
 import okhttp3.OkHttpClient
 import okhttp3.Request
 import org.koin.core.KoinComponent
@@ -11,6 +15,8 @@ import org.koitharu.kotatsu.core.model.MangaPage
 import org.koitharu.kotatsu.core.prefs.ReaderMode
 import org.koitharu.kotatsu.utils.ext.await
 import org.koitharu.kotatsu.utils.ext.medianOrNull
+import org.koitharu.kotatsu.utils.ext.use
+import java.io.File
 import java.io.InputStream
 
 object MangaUtils : KoinComponent {
@@ -54,4 +60,81 @@ object MangaUtils : KoinComponent {
 		check(imageHeight > 0 && imageWidth > 0)
 		return Size(imageWidth, imageHeight)
 	}
+
+	@JvmStatic
+	fun cropBitmap(input: Bitmap): Bitmap? {
+		return try {
+			val bounds = Rect(0, 0, input.width, input.height)
+			var isBoundsChanged = false
+			for (x in 1 until input.width / 2) {
+				var leftColor = 0
+				var rightColor = 0
+				for (y in 0 until input.height) {
+					leftColor += input[x, y]
+					rightColor += input[input.width - x - 1, y]
+				}
+				leftColor /= input.height
+				rightColor /= input.height
+				var consumed = false
+				if (leftColor == Color.WHITE) {
+					bounds.left++
+					consumed = true
+				}
+				if (rightColor == Color.WHITE) {
+					bounds.right--
+					consumed = true
+				}
+				if (consumed) {
+					isBoundsChanged = true
+				} else {
+					break
+				}
+			}
+			for (y in 1 until input.height / 2) {
+				var topColor = 0
+				var bottomColor = 0
+				for (x in 0 until input.width) {
+					topColor += input[x, y]
+					bottomColor += input[x, input.height - y - 1]
+				}
+				topColor /= input.width
+				bottomColor /= input.width
+				var consumed = false
+				if (topColor == Color.WHITE) {
+					bounds.top++
+					consumed = true
+				}
+				if (bottomColor == Color.WHITE) {
+					bounds.bottom--
+					consumed = true
+				}
+				if (consumed) {
+					isBoundsChanged = true
+				} else {
+					break
+				}
+			}
+			if (isBoundsChanged) {
+				Bitmap.createBitmap(input, bounds.left, bounds.top, bounds.width(), bounds.height())
+			} else {
+				null
+			}
+		} catch (e: Throwable) {
+			if (BuildConfig.DEBUG) {
+				e.printStackTrace()
+			}
+			null
+		}
+	}
+
+	@JvmStatic
+	fun cropBitmap(file: File) {
+		BitmapFactory.decodeFile(file.path).use { bmp ->
+			cropBitmap(bmp)?.use { cropped ->
+				file.outputStream().use { out ->
+					cropped.compress(Bitmap.CompressFormat.WEBP, 100, out)
+				}
+			}
+		}
+	}
 }

app/src/main/java/org/koitharu/kotatsu/ui/reader/PageLoader.kt

@@ -1,7 +1,9 @@
 package org.koitharu.kotatsu.ui.reader
 
 import android.net.Uri
+import androidx.annotation.WorkerThread
 import kotlinx.coroutines.*
+import kotlinx.coroutines.sync.Mutex
 import okhttp3.OkHttpClient
 import okhttp3.Request
 import org.koin.core.KoinComponent
@@ -16,13 +18,14 @@ import kotlin.coroutines.CoroutineContext
 class PageLoader : KoinComponent, CoroutineScope, DisposableHandle {
 
 	private val job = SupervisorJob()
-	private val tasks = HashMap<String, Job>()
+	private val mutex = Mutex()
 	private val okHttp by inject<OkHttpClient>()
 	private val cache by inject<PagesCache>()
 
 	override val coroutineContext: CoroutineContext
 		get() = Dispatchers.Main + job
 
+	@WorkerThread
 	@Suppress("BlockingMethodInNonBlockingContext")
 	suspend fun loadFile(url: String, force: Boolean): File {
 		if (!force) {
@@ -55,6 +58,10 @@ class PageLoader : KoinComponent, CoroutineScope, DisposableHandle {
 					response.body!!.byteStream().copyTo(out)
 				}
 			}
+		}.also {
+			mutex.withLock(this) {
+				MangaUtils.cropBitmap(it)
+			}
 		}
 	}
 

app/src/main/java/org/koitharu/kotatsu/utils/ext/CommonExt.kt

@@ -1,6 +1,7 @@
 package org.koitharu.kotatsu.utils.ext
 
 import android.content.res.Resources
+import android.graphics.Bitmap
 import kotlinx.coroutines.delay
 import org.koitharu.kotatsu.BuildConfig
 import org.koitharu.kotatsu.R
@@ -43,4 +44,10 @@ fun Throwable.getDisplayMessage(resources: Resources) = when (this) {
 	} else {
 		resources.getString(R.string.error_occurred)
 	}
+}
+
+inline fun <R> Bitmap.use(block: (Bitmap) -> R): R = try {
+	block(this)
+} finally {
+	recycle()
 }