tiling improvements (WIP)

android/app/src/main/kotlin/deckers/thibault/aves/channel/calls/ImageFileHandler.kt

@@ -20,6 +20,8 @@ import kotlin.math.roundToInt
 class ImageFileHandler(private val activity: Activity) : MethodCallHandler {
     private val density = activity.resources.displayMetrics.density
 
+    private val regionFetcher = RegionFetcher(activity)
+
     override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
         when (call.method) {
             "getObsoleteEntries" -> GlobalScope.launch { getObsoleteEntries(call, Coresult(result)) }
@@ -90,14 +92,13 @@ class ImageFileHandler(private val activity: Activity) : MethodCallHandler {
             return
         }
 
-        RegionFetcher(
+        regionFetcher.fetch(
-            activity,
             uri,
             mimeType,
             sampleSize,
             Rect(x, y, x + width, y + height),
             result,
-        ).fetch()
+        )
     }
 
     private suspend fun getImageEntry(call: MethodCall, result: MethodChannel.Result) {

android/app/src/main/kotlin/deckers/thibault/aves/channel/calls/RegionFetcher.kt

@@ -1,50 +1,67 @@
 package deckers.thibault.aves.channel.calls
 
-import android.app.Activity
+import android.content.Context
 import android.graphics.Bitmap
 import android.graphics.BitmapFactory
 import android.graphics.BitmapRegionDecoder
 import android.graphics.Rect
 import android.net.Uri
+import android.util.Log
 import deckers.thibault.aves.utils.MimeTypes
 import deckers.thibault.aves.utils.StorageUtils
 import io.flutter.plugin.common.MethodChannel
 import java.io.ByteArrayOutputStream
 
 class RegionFetcher internal constructor(
-    private val activity: Activity,
+    private val context: Context,
-    private val uri: Uri,
-    private val mimeType: String,
-    private val sampleSize: Int,
-    private val rect: Rect,
-    private val result: MethodChannel.Result,
 ) {
+    private var lastDecoderRef: Pair<Uri, BitmapRegionDecoder>? = null
 
-    fun fetch() {
+    fun fetch(
-        val options = BitmapFactory.Options().apply { inSampleSize = sampleSize }
+        uri: Uri,
+        mimeType: String,
+        sampleSize: Int,
+        rect: Rect,
+        result: MethodChannel.Result,
+    ) {
+        val options = BitmapFactory.Options().apply {
+            inSampleSize = sampleSize
+        }
+
+        var currentDecoderRef = lastDecoderRef
+        if (currentDecoderRef != null && currentDecoderRef.first != uri) {
+            currentDecoderRef.second.recycle()
+            currentDecoderRef = null
+        }
 
         try {
-            StorageUtils.openInputStream(activity, uri).use { input ->
+            if (currentDecoderRef == null) {
-                val decoder = BitmapRegionDecoder.newInstance(input, false)
+                val newDecoder = StorageUtils.openInputStream(context, uri).use { input ->
-                val data = decoder.decodeRegion(rect, options)?.let {
+                    BitmapRegionDecoder.newInstance(input, false)
-                    val stream = ByteArrayOutputStream()
-                    // we compress the bitmap because Dart Image.memory cannot decode the raw bytes
-                    // Bitmap.CompressFormat.PNG is slower than JPEG, but it allows transparency
-                    if (MimeTypes.canHaveAlpha(mimeType)) {
-                        it.compress(Bitmap.CompressFormat.PNG, 0, stream)
-                    } else {
-                        it.compress(Bitmap.CompressFormat.JPEG, 100, stream)
-                    }
-                    stream.toByteArray()
                 }
-                if (data != null) {
+                currentDecoderRef = Pair(uri, newDecoder)
-                    result.success(data)
+            }
+            val decoder = currentDecoderRef.second
+            lastDecoderRef = currentDecoderRef
+
+            val data = decoder.decodeRegion(rect, options)?.let {
+                val stream = ByteArrayOutputStream()
+                // we compress the bitmap because Dart Image.memory cannot decode the raw bytes
+                // Bitmap.CompressFormat.PNG is slower than JPEG, but it allows transparency
+                if (MimeTypes.canHaveAlpha(mimeType)) {
+                    it.compress(Bitmap.CompressFormat.PNG, 0, stream)
                 } else {
-                    result.error("getRegion-null", "failed to decode region for uri=$uri rect=$rect", null)
+                    it.compress(Bitmap.CompressFormat.JPEG, 100, stream)
                 }
+                stream.toByteArray()
+            }
+            if (data != null) {
+                result.success(data)
+            } else {
+                result.error("getRegion-null", "failed to decode region for uri=$uri rect=$rect", null)
             }
         } catch (e: Exception) {
-            result.error("getRegion-read-exception", "failed to get image from uri=$uri", e.message)
+            result.error("getRegion-read-exception", "failed to initialize region decoder for uri=$uri", e.message)
         }
     }
 }

lib/utils/math_utils.dart

@@ -2,6 +2,10 @@ import 'dart:math';
 
 const double _piOver180 = pi / 180.0;
 
-double toDegrees(double radians) => radians / _piOver180;
+final double log2 = log(2);
 
-double toRadians(double degrees) => degrees * _piOver180;
+double toDegrees(num radians) => radians / _piOver180;
+
+double toRadians(num degrees) => degrees * _piOver180;
+
+int highestPowerOf2(num x) => x < 1 ? 0 : pow(2, (log(x) / log2).floor());

lib/widgets/fullscreen/image_view.dart

@@ -43,6 +43,7 @@ class _ImageViewState extends State<ImageView> {
   StreamSubscription<PhotoViewControllerValue> _subscription;
 
   static const backgroundDecoration = BoxDecoration(color: Colors.transparent);
+  static const maxScale = 2.0;
 
   ImageEntry get entry => widget.entry;
 
@@ -140,6 +141,7 @@ class _ImageViewState extends State<ImageView> {
       loadFailedChild: _buildError(),
       backgroundDecoration: backgroundDecoration,
       controller: _photoViewController,
+      maxScale: maxScale,
       minScale: PhotoViewComputedScale.contained,
       initialScale: PhotoViewComputedScale.contained,
       onTapUp: (tapContext, details, value) => onTap?.call(),
@@ -166,6 +168,7 @@ class _ImageViewState extends State<ImageView> {
       childSize: entry.displaySize,
       backgroundDecoration: backgroundDecoration,
       controller: _photoViewController,
+      maxScale: maxScale,
       minScale: PhotoViewComputedScale.contained,
       initialScale: PhotoViewComputedScale.contained,
       onTapUp: (tapContext, details, value) => onTap?.call(),
@@ -204,6 +207,7 @@ class _ImageViewState extends State<ImageView> {
       childSize: entry.displaySize,
       backgroundDecoration: backgroundDecoration,
       controller: _photoViewController,
+      maxScale: maxScale,
       minScale: PhotoViewComputedScale.contained,
       initialScale: PhotoViewComputedScale.contained,
       onTapUp: (tapContext, details, value) => onTap?.call(),

lib/widgets/fullscreen/tiled_view.dart

@@ -27,8 +27,9 @@ class TiledImageView extends StatefulWidget {
 }
 
 class _TiledImageViewState extends State<TiledImageView> {
-  double _initialScale;
+  double _tileSide, _initialScale;
   int _maxSampleSize;
+  Matrix4 _transform;
 
   ImageEntry get entry => widget.entry;
 
@@ -36,10 +37,11 @@ class _TiledImageViewState extends State<TiledImageView> {
 
   ValueNotifier<ViewState> get viewStateNotifier => widget.viewStateNotifier;
 
-  static const tileSide = 200.0;
-
   // margin around visible area to fetch surrounding tiles in advance
-  static const preFetchMargin = 50.0;
+  static const preFetchMargin = 0.0;
+
+  // magic number used to derive sample size from scale
+  static const scaleFactor = 2.0;
 
   @override
   void initState() {
@@ -57,8 +59,20 @@ class _TiledImageViewState extends State<TiledImageView> {
   }
 
   void _init() {
+    _tileSide = viewportSize.shortestSide * scaleFactor;
     _initialScale = min(viewportSize.width / entry.displaySize.width, viewportSize.height / entry.displaySize.height);
     _maxSampleSize = _sampleSizeForScale(_initialScale);
+
+    final rotationDegrees = entry.rotationDegrees;
+    final isFlipped = entry.isFlipped;
+    _transform = null;
+    if (rotationDegrees != 0 || isFlipped) {
+      _transform = Matrix4.identity()
+        ..translate(entry.width / 2.0, entry.height / 2.0)
+        ..scale(isFlipped ? -1.0 : 1.0, 1.0, 1.0)
+        ..rotateZ(-toRadians(rotationDegrees.toDouble()))
+        ..translate(-entry.displaySize.width / 2.0, -entry.displaySize.height / 2.0);
+    }
   }
 
   @override
@@ -67,16 +81,6 @@ class _TiledImageViewState extends State<TiledImageView> {
 
     final displayWidth = entry.displaySize.width;
     final displayHeight = entry.displaySize.height;
-    final rotationDegrees = entry.rotationDegrees;
-    final isFlipped = entry.isFlipped;
-    Matrix4 transform;
-    if (rotationDegrees != 0 || isFlipped) {
-      transform = Matrix4.identity()
-        ..translate(entry.width / 2.0, entry.height / 2.0)
-        ..scale(isFlipped ? -1.0 : 1.0, 1.0, 1.0)
-        ..rotateZ(-toRadians(rotationDegrees.toDouble()))
-        ..translate(-displayWidth / 2.0, -displayHeight / 2.0);
-    }
 
     return AnimatedBuilder(
         animation: viewStateNotifier,
@@ -98,7 +102,7 @@ class _TiledImageViewState extends State<TiledImageView> {
           final tiles = <Widget>[];
           var minSampleSize = min(_sampleSizeForScale(scale), _maxSampleSize);
           for (var sampleSize = _maxSampleSize; sampleSize >= minSampleSize; sampleSize = (sampleSize / 2).floor()) {
-            final layerRegionSize = Size.square(tileSide * sampleSize);
+            final layerRegionSize = Size.square(_tileSide * sampleSize);
             for (var x = 0.0; x < displayWidth; x += layerRegionSize.width) {
               for (var y = 0.0; y < displayHeight; y += layerRegionSize.height) {
                 final regionOrigin = Offset(x, y);
@@ -114,10 +118,10 @@ class _TiledImageViewState extends State<TiledImageView> {
                   var regionRect = regionOrigin & thisRegionSize;
 
                   // apply EXIF orientation
-                  if (transform != null) {
+                  if (_transform != null) {
                     regionRect = Rect.fromPoints(
-                      MatrixUtils.transformPoint(transform, regionRect.topLeft),
+                      MatrixUtils.transformPoint(_transform, regionRect.topLeft),
-                      MatrixUtils.transformPoint(transform, regionRect.bottomRight),
+                      MatrixUtils.transformPoint(_transform, regionRect.bottomRight),
                     );
                   }
 
@@ -149,7 +153,7 @@ class _TiledImageViewState extends State<TiledImageView> {
   int _sampleSizeForScale(double scale) {
     var sample = 0;
     if (0 < scale && scale < 1) {
-      sample = pow(2, (log(1 / scale) / log(2)).floor());
+      sample = highestPowerOf2((1 / scale) / scaleFactor);
     }
     return max<int>(1, sample);
   }
@@ -157,6 +161,7 @@ class _TiledImageViewState extends State<TiledImageView> {
 
 class RegionTile extends StatelessWidget {
   final ImageEntry entry;
+
   // `tileRect` uses Flutter view coordinates
   // `regionRect` uses the raw image pixel coordinates
   final Rect tileRect, regionRect;