Load image file as pixel by Android uri

plugin/android/src/main/kotlin/com/nkming/nc_photos/plugin/ImageLoaderChannelHandler.kt

@@ -0,0 +1,65 @@
+package com.nkming.nc_photos.plugin
+
+import android.content.Context
+import android.net.Uri
+import com.nkming.nc_photos.plugin.image_processor.Rgba8Image
+import com.nkming.nc_photos.plugin.image_processor.TfLiteHelper
+import io.flutter.plugin.common.MethodCall
+import io.flutter.plugin.common.MethodChannel
+
+class ImageLoaderChannelHandler(context: Context) :
+	MethodChannel.MethodCallHandler {
+	companion object {
+		const val METHOD_CHANNEL = "${K.LIB_ID}/image_loader_method"
+	}
+
+	override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
+		when (call.method) {
+			"loadUri" -> {
+				try {
+					loadUri(
+						call.argument("fileUri")!!,
+						call.argument("maxWidth")!!,
+						call.argument("maxHeight")!!,
+						call.argument("resizeMethod")!!,
+						call.argument("isAllowSwapSide")!!,
+						call.argument("shouldUpscale")!!,
+						result
+					)
+				} catch (e: Throwable) {
+					result.error("systemException", e.toString(), null)
+				}
+			}
+
+			else -> result.notImplemented()
+		}
+	}
+
+	/**
+	 * Load and resize an image pointed by a uri
+	 *
+	 * @param fileUri
+	 * @param maxWidth
+	 * @param maxHeight
+	 * @param resizeMethod
+	 * @param isAllowSwapSide
+	 * @param shouldUpscale
+	 * @param result
+	 */
+	private fun loadUri(
+		fileUri: String, maxWidth: Int, maxHeight: Int, resizeMethod: Int,
+		isAllowSwapSide: Boolean, shouldUpscale: Boolean,
+		result: MethodChannel.Result
+	) {
+		val image = BitmapUtil.loadImage(
+			context, Uri.parse(fileUri), maxWidth, maxHeight,
+			BitmapResizeMethod.values()[resizeMethod], isAllowSwapSide,
+			shouldUpscale
+		).use {
+			Rgba8Image(TfLiteHelper.bitmapToRgba8Array(it), it.width, it.height)
+		}
+		result.success(image.toJson())
+	}
+
+	private val context = context
+}

plugin/android/src/main/kotlin/com/nkming/nc_photos/plugin/NcPhotosPlugin.kt

@@ -113,6 +113,14 @@ class NcPhotosPlugin : FlutterPlugin, ActivityAware,
 			PreferenceChannelHandler.METHOD_CHANNEL
 		)
 		preferenceMethodChannel.setMethodCallHandler(preferenceChannelHandler)
+
+		val imageLoaderChannelHandler =
+			ImageLoaderChannelHandler(flutterPluginBinding.applicationContext)
+		imageLoaderMethodChannel = MethodChannel(
+			flutterPluginBinding.binaryMessenger,
+			ImageLoaderChannelHandler.METHOD_CHANNEL
+		)
+		imageLoaderMethodChannel.setMethodCallHandler(imageLoaderChannelHandler)
 	}
 
 	override fun onDetachedFromEngine(
@@ -131,6 +139,7 @@ class NcPhotosPlugin : FlutterPlugin, ActivityAware,
 		permissionMethodChannel.setMethodCallHandler(null)
 		logcatMethodChannel.setMethodCallHandler(null)
 		preferenceMethodChannel.setMethodCallHandler(null)
+		imageLoaderMethodChannel.setMethodCallHandler(null)
 	}
 
 	override fun onAttachedToActivity(binding: ActivityPluginBinding) {
@@ -219,6 +228,7 @@ class NcPhotosPlugin : FlutterPlugin, ActivityAware,
 	private lateinit var permissionMethodChannel: MethodChannel
 	private lateinit var logcatMethodChannel: MethodChannel
 	private lateinit var preferenceMethodChannel: MethodChannel
+	private lateinit var imageLoaderMethodChannel: MethodChannel
 
 	private lateinit var lockChannelHandler: LockChannelHandler
 	private lateinit var mediaStoreChannelHandler: MediaStoreChannelHandler

plugin/android/src/main/kotlin/com/nkming/nc_photos/plugin/image_processor/Image.kt

@@ -0,0 +1,33 @@
+package com.nkming.nc_photos.plugin.image_processor
+
+import android.graphics.Bitmap
+import java.nio.ByteBuffer
+
+/**
+ * Container of pixel data stored in RGBA format
+ */
+class Rgba8Image(val pixel: ByteArray, val width: Int, val height: Int) {
+	companion object {
+		fun fromJson(json: Map<String, Any>) = Rgba8Image(
+			json["pixel"] as ByteArray, json["width"] as Int,
+			json["height"] as Int
+		)
+	}
+
+	fun toJson() = mapOf<String, Any>(
+		"pixel" to pixel,
+		"width" to width,
+		"height" to height,
+	)
+
+	fun toBitmap(): Bitmap {
+		return Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888)
+			.apply {
+				copyPixelsFromBuffer(ByteBuffer.wrap(pixel))
+			}
+	}
+
+	init {
+		assert(pixel.size == width * height * 4)
+	}
+}

plugin/android/src/main/kotlin/com/nkming/nc_photos/plugin/image_processor/TfLiteHelper.kt

@@ -1,6 +1,7 @@
 package com.nkming.nc_photos.plugin.image_processor
 
 import android.graphics.Bitmap
+import java.nio.ByteBuffer
 import java.nio.IntBuffer
 
 interface TfLiteHelper {
@@ -25,6 +26,18 @@ interface TfLiteHelper {
 			return rgb8
 		}
 
+		/**
+		 * Convert an ARGB_8888 Android bitmap to a RGBA byte array
+		 *
+		 * @param bitmap
+		 * @return
+		 */
+		fun bitmapToRgba8Array(bitmap: Bitmap): ByteArray {
+			val buffer = ByteBuffer.allocate(bitmap.width * bitmap.height * 4)
+			bitmap.copyPixelsToBuffer(buffer)
+			return buffer.array()
+		}
+
 		/**
 		 * Convert a RGB8 byte array to an ARGB_8888 Android bitmap
 		 *

plugin/lib/nc_photos_plugin.dart

@@ -2,6 +2,8 @@ library nc_photos_plugin;
 
 export 'src/content_uri.dart';
 export 'src/exception.dart';
+export 'src/image.dart';
+export 'src/image_loader.dart';
 export 'src/image_processor.dart';
 export 'src/lock.dart';
 export 'src/logcat.dart';

plugin/lib/src/image.dart

@@ -0,0 +1,22 @@
+import 'dart:typed_data';
+
+/// Container of pixel data stored in RGBA format
+class Rgba8Image {
+  const Rgba8Image(this.pixel, this.width, this.height);
+
+  factory Rgba8Image.fromJson(Map<String, dynamic> json) => Rgba8Image(
+        json["pixel"],
+        json["width"],
+        json["height"],
+      );
+
+  Map<String, dynamic> toJson() => {
+        "pixel": pixel,
+        "width": width,
+        "height": height,
+      };
+
+  final Uint8List pixel;
+  final int width;
+  final int height;
+}

plugin/lib/src/image_loader.dart

@@ -0,0 +1,34 @@
+import 'dart:async';
+
+import 'package:flutter/services.dart';
+import 'package:nc_photos_plugin/src/image.dart';
+import 'package:nc_photos_plugin/src/k.dart' as k;
+
+enum ImageLoaderResizeMethod {
+  fit,
+  fill,
+}
+
+class ImageLoader {
+  static Future<Rgba8Image> loadUri(
+    String fileUri,
+    int maxWidth,
+    int maxHeight,
+    ImageLoaderResizeMethod resizeMethod, {
+    bool isAllowSwapSide = false,
+    bool shouldUpscale = false,
+  }) async {
+    final result =
+        await _methodChannel.invokeMethod<Map>("loadUri", <String, dynamic>{
+      "fileUri": fileUri,
+      "maxWidth": maxWidth,
+      "maxHeight": maxHeight,
+      "resizeMethod": resizeMethod.index,
+      "isAllowSwapSide": isAllowSwapSide,
+      "shouldUpscale": shouldUpscale,
+    });
+    return Rgba8Image.fromJson(result!.cast<String, dynamic>());
+  }
+
+  static const _methodChannel = MethodChannel("${k.libId}/image_loader_method");
+}