Fix pages thumbnails for webtoons

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

@@ -13,6 +13,7 @@ import com.google.android.material.progressindicator.BaseProgressIndicator
 import okhttp3.HttpUrl.Companion.toHttpUrlOrNull
 import org.koitharu.kotatsu.R
 import org.koitharu.kotatsu.core.network.CommonHeaders
+import org.koitharu.kotatsu.utils.image.RegionBitmapDecoder
 import org.koitharu.kotatsu.utils.progress.ImageRequestIndicatorListener
 
 fun ImageView.newImageRequest(url: Any?): ImageRequest.Builder? {
@@ -66,6 +67,10 @@ fun ImageRequest.Builder.indicator(indicator: BaseProgressIndicator<*>): ImageRe
 	return listener(ImageRequestIndicatorListener(indicator))
 }
 
+fun ImageRequest.Builder.decodeRegion(): ImageRequest.Builder {
+	return decoderFactory(RegionBitmapDecoder.Factory())
+}
+
 @Suppress("SpellCheckingInspection")
 fun ImageRequest.Builder.crossfade(context: Context?): ImageRequest.Builder {
 	if (context == null) {

app/src/main/java/org/koitharu/kotatsu/utils/image/RegionBitmapDecoder.kt

@@ -0,0 +1,168 @@
+package org.koitharu.kotatsu.utils.image
+
+import android.graphics.Bitmap
+import android.graphics.BitmapFactory
+import android.graphics.BitmapRegionDecoder
+import android.graphics.Rect
+import android.os.Build
+import androidx.core.graphics.drawable.toDrawable
+import coil.ImageLoader
+import coil.decode.DecodeResult
+import coil.decode.DecodeUtils
+import coil.decode.Decoder
+import coil.decode.ImageSource
+import coil.fetch.SourceResult
+import coil.request.Options
+import coil.size.*
+import kotlin.math.roundToInt
+import kotlinx.coroutines.runInterruptible
+import kotlinx.coroutines.sync.Semaphore
+import kotlinx.coroutines.sync.withPermit
+
+class RegionBitmapDecoder(
+	private val source: ImageSource,
+	private val options: Options,
+	private val parallelismLock: Semaphore,
+) : Decoder {
+
+	override suspend fun decode() = parallelismLock.withPermit {
+		runInterruptible { BitmapFactory.Options().decode() }
+	}
+
+	private fun BitmapFactory.Options.decode(): DecodeResult {
+		val regionDecoder = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
+			BitmapRegionDecoder.newInstance(source.source().inputStream())
+		} else {
+			@Suppress("DEPRECATION")
+			BitmapRegionDecoder.newInstance(source.source().inputStream(), false)
+		}
+		checkNotNull(regionDecoder)
+		try {
+			val rect = configureScale(regionDecoder.width, regionDecoder.height)
+			configureConfig()
+			val bitmap = regionDecoder.decodeRegion(rect, this)
+			bitmap.density = options.context.resources.displayMetrics.densityDpi
+			return DecodeResult(
+				drawable = bitmap.toDrawable(options.context.resources),
+				isSampled = true,
+			)
+		} finally {
+			regionDecoder.recycle()
+		}
+	}
+
+	private fun BitmapFactory.Options.configureConfig() {
+		var config = options.config
+
+		inMutable = false
+
+		if (Build.VERSION.SDK_INT >= 26 && options.colorSpace != null) {
+			inPreferredColorSpace = options.colorSpace
+		}
+		inPremultiplied = options.premultipliedAlpha
+
+		// Decode the image as RGB_565 as an optimization if allowed.
+		if (options.allowRgb565 && config == Bitmap.Config.ARGB_8888 && outMimeType == "image/jpeg") {
+			config = Bitmap.Config.RGB_565
+		}
+
+		// High color depth images must be decoded as either RGBA_F16 or HARDWARE.
+		if (Build.VERSION.SDK_INT >= 26 && outConfig == Bitmap.Config.RGBA_F16 && config != Bitmap.Config.HARDWARE) {
+			config = Bitmap.Config.RGBA_F16
+		}
+
+		inPreferredConfig = config
+	}
+
+	/** Compute and set the scaling properties for [BitmapFactory.Options]. */
+	private fun BitmapFactory.Options.configureScale(srcWidth: Int, srcHeight: Int): Rect {
+		val dstWidth = options.size.widthPx(options.scale) { srcWidth }
+		val dstHeight = options.size.heightPx(options.scale) { srcHeight }
+
+		val srcRatio = srcWidth / srcHeight.toDouble()
+		val dstRatio = dstWidth / dstHeight.toDouble()
+		val rect = if (srcRatio < dstRatio) {
+			// probably manga
+			Rect(0, 0, srcWidth, (srcWidth / dstRatio).toInt())
+		} else {
+			Rect(0, 0, (srcHeight / dstRatio).toInt(), srcHeight)
+		}
+		rect.offsetTo(
+			(srcWidth - rect.width()) / 2,
+			(srcHeight - rect.height()) / 2,
+		)
+
+		// Calculate the image's sample size.
+		inSampleSize = DecodeUtils.calculateInSampleSize(
+			srcWidth = rect.width(),
+			srcHeight = rect.height(),
+			dstWidth = dstWidth,
+			dstHeight = dstHeight,
+			scale = options.scale,
+		)
+
+		// Calculate the image's density scaling multiple.
+		var scale = DecodeUtils.computeSizeMultiplier(
+			srcWidth = rect.width() / inSampleSize.toDouble(),
+			srcHeight = rect.height() / inSampleSize.toDouble(),
+			dstWidth = dstWidth.toDouble(),
+			dstHeight = dstHeight.toDouble(),
+			scale = options.scale,
+		)
+
+		// Only upscale the image if the options require an exact size.
+		if (options.allowInexactSize) {
+			scale = scale.coerceAtMost(1.0)
+		}
+
+		inScaled = scale != 1.0
+		if (inScaled) {
+			if (scale > 1) {
+				// Upscale
+				inDensity = (Int.MAX_VALUE / scale).roundToInt()
+				inTargetDensity = Int.MAX_VALUE
+			} else {
+				// Downscale
+				inDensity = Int.MAX_VALUE
+				inTargetDensity = (Int.MAX_VALUE * scale).roundToInt()
+			}
+		}
+		return rect
+	}
+
+	class Factory(
+		maxParallelism: Int = DEFAULT_MAX_PARALLELISM,
+	) : Decoder.Factory {
+
+		@Suppress("NEWER_VERSION_IN_SINCE_KOTLIN")
+		@SinceKotlin("999.9") // Only public in Java.
+		constructor() : this()
+
+		private val parallelismLock = Semaphore(maxParallelism)
+
+		override fun create(result: SourceResult, options: Options, imageLoader: ImageLoader): Decoder {
+			return RegionBitmapDecoder(result.source, options, parallelismLock)
+		}
+
+		override fun equals(other: Any?) = other is Factory
+
+		override fun hashCode() = javaClass.hashCode()
+	}
+}
+
+private const val DEFAULT_MAX_PARALLELISM = 4
+
+private inline fun Size.widthPx(scale: Scale, original: () -> Int): Int {
+	return if (isOriginal) original() else width.toPx(scale)
+}
+
+private inline fun Size.heightPx(scale: Scale, original: () -> Int): Int {
+	return if (isOriginal) original() else height.toPx(scale)
+}
+
+private fun Dimension.toPx(scale: Scale) = pxOrElse {
+	when (scale) {
+		Scale.FILL -> Int.MIN_VALUE
+		Scale.FIT -> Int.MAX_VALUE
+	}
+}