image redrawing api

build.gradle

@@ -59,6 +59,7 @@ dependencies {
 	api 'org.jsoup:jsoup:1.17.2'
 	implementation 'org.json:json:20240303'
 	implementation 'androidx.collection:collection:1.4.0'
+	implementation 'org.jetbrains.kotlinx:kotlinx-io-core:0.3.4'
 
 	ksp project(':kotatsu-parsers-ksp')
 

src/main/kotlin/org/koitharu/kotatsu/parsers/MangaLoaderContext.kt

@@ -2,6 +2,8 @@ package org.koitharu.kotatsu.parsers
 
 import okhttp3.CookieJar
 import okhttp3.OkHttpClient
+import okhttp3.Response
+import org.koitharu.kotatsu.parsers.bitmap.Bitmap
 import org.koitharu.kotatsu.parsers.config.MangaSourceConfig
 import org.koitharu.kotatsu.parsers.model.MangaSource
 import java.util.*
@@ -31,4 +33,15 @@ abstract class MangaLoaderContext {
 	abstract fun getConfig(source: MangaSource): MangaSourceConfig
 
 	abstract fun getDefaultUserAgent(): String
+
+	/**
+	 * Helper function to be used in an interceptor
+	 * to descramble images
+	 * @param response Image response
+	 * @param redraw lambda function to implement descrambling logic
+	 */
+	abstract fun redrawImageResponse(
+		response: Response,
+		redraw: (image: Bitmap) -> Bitmap
+	): Response
 }

src/main/kotlin/org/koitharu/kotatsu/parsers/bitmap/Bitmap.kt

@@ -0,0 +1,53 @@
+package org.koitharu.kotatsu.parsers.bitmap
+
+import kotlinx.io.Sink
+
+abstract class Bitmap {
+	abstract val width: Int
+	abstract val height: Int
+
+	enum class CompressFormat {
+		JPEG,
+		PNG,
+		WEBP_LOSSY,
+		WEBP_LOSSLESS,
+	}
+
+	enum class Config {
+		ALPHA_8,
+		RGB_565,
+		ARGB_8888,
+		RGBA_F16,
+		HARDWARE,
+		RGBA_1010102,
+	}
+
+	abstract fun compress(
+		format: CompressFormat,
+		quality: Int,
+		sink: Sink
+	): Boolean
+
+	abstract fun getPixels(
+		/*@ColorInt*/
+		pixels: IntArray,
+		offset: Int,
+		stride: Int,
+		x: Int,
+		y: Int,
+		width: Int,
+		height: Int,
+	)
+
+	abstract fun drawBitmap(sourceBitmap: Bitmap, src: Rect, dst: Rect)
+
+	companion object {
+		fun createBitmap(width: Int, height: Int, config: Config): Bitmap {
+			throw NotImplementedError("createBitmap(width, height, config) is not implemented")
+		}
+
+		fun createBitmap(source: Bitmap, x: Int, y: Int, width: Int, height: Int): Bitmap {
+			throw NotImplementedError("createBitmap(source, x, y, width, height) is not implemented")
+		}
+	}
+}

src/main/kotlin/org/koitharu/kotatsu/parsers/bitmap/Rect.kt

@@ -0,0 +1,13 @@
+package org.koitharu.kotatsu.parsers.bitmap
+
+data class Rect(
+	val left: Int = 0,
+	val top: Int = 0,
+	val right: Int = 0,
+	val bottom: Int = 0,
+) {
+	val width: Int
+		get() = right - left
+	val height: Int
+		get() = bottom - top
+}

src/main/kotlin/org/koitharu/kotatsu/parsers/site/all/MangaReaderToParser.kt

@@ -1,18 +1,16 @@
 package org.koitharu.kotatsu.parsers.site.all
 
-import android.graphics.*
 import okhttp3.HttpUrl.Companion.toHttpUrl
 import okhttp3.Interceptor
-import okhttp3.MediaType.Companion.toMediaType
 import okhttp3.Response
-import okhttp3.ResponseBody.Companion.toResponseBody
 import org.jsoup.Jsoup
 import org.jsoup.nodes.Document
 import org.koitharu.kotatsu.parsers.*
+import org.koitharu.kotatsu.parsers.bitmap.Bitmap
+import org.koitharu.kotatsu.parsers.bitmap.Rect
 import org.koitharu.kotatsu.parsers.config.ConfigKey
 import org.koitharu.kotatsu.parsers.model.*
 import org.koitharu.kotatsu.parsers.util.*
-import java.io.*
 import java.util.*
 import javax.crypto.Cipher
 import javax.crypto.spec.SecretKeySpec
@@ -258,22 +256,17 @@ class MangaReaderToParser(context: MangaLoaderContext) : PagedMangaParser(contex
 		val response = chain.proceed(request)
 
 		if (request.url.fragment != "scrambled") return response
-		val image = response.body!!.byteStream().use(::descramble)
-		val body = image.toResponseBody("image/jpeg".toMediaType())
-		return response.newBuilder()
-			.body(body)
-			.build()
+
+		return context.redrawImageResponse(response, ::descramble)
 	}
 
 	private val memo = hashMapOf<Int, IntArray>()
 
-	private fun descramble(image: InputStream): ByteArray {
-		val bitmap = BitmapFactory.decodeStream(image)
+	private fun descramble(bitmap: Bitmap): Bitmap {
 		val width = bitmap.width
 		val height = bitmap.height
 
 		val result = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888)
-		val canvas = Canvas(result)
 
 		val pieces = ArrayList<Piece>()
 		for (y in 0 until height step PIECE_SIZE) {
@@ -304,13 +297,11 @@ class MangaReaderToParser(context: MangaLoaderContext) : PagedMangaParser(contex
 				val srcRect = Rect(src.x, src.y, src.x + src.w, src.y + src.h)
 				val dstRect = Rect(dst.x, dst.y, dst.x + dst.w, dst.y + dst.h)
 
-				canvas.drawBitmap(bitmap, srcRect, dstRect, null)
+				result.drawBitmap(bitmap, srcRect, dstRect)
 			}
 		}
 
-		val output = ByteArrayOutputStream()
-		result.compress(Bitmap.CompressFormat.JPEG, 90, output)
-		return output.toByteArray()
+		return result
 	}
 
 	private class Piece(val x: Int, val y: Int, val w: Int, val h: Int)