make reading of images a native module

android/app/src/main/java/com/jellify/BackgroundFileReader.kt

@@ -0,0 +1,15 @@
+@ReactMethod
+public void readBlobInBackground(ReadableMap blob, Promise promise) {
+  new Thread(new Runnable() {
+    @Override
+    public void run() {
+      try {
+        byte[] bytes = Base64.decode(blob.getString("data"), Base64.DEFAULT);
+        String base64String = Base64.encodeToString(bytes, Base64.NO_WRAP);
+        promise.resolve(base64String);
+      } catch (Exception e) {
+        promise.reject("Error", e);
+      }
+    }
+  }).start();
+}

api/queries/functions/images.ts

@@ -2,8 +2,9 @@ import { ImageFormat, ImageType } from "@jellyfin/sdk/lib/generated-client/model
 import { getImageApi } from "@jellyfin/sdk/lib/utils/api"
 import _ from "lodash"
 import Client from "../../../api/client"
-import { backgroundRuntime } from "../../../App";
-import { runOnRuntime } from "react-native-reanimated";
+import { NativeModules } from "react-native";
+
+const { BackgroundFileReader } = NativeModules;
 
 export function fetchItemImage(itemId: string, imageType: ImageType, width: number, height: number) {
     
@@ -40,13 +41,7 @@ export function fetchItemImage(itemId: string, imageType: ImageType, width: numb
 }
 
 function blobToBase64(blob : Blob) {
-    return new Promise<string>((resolve, _) => {
-        runOnRuntime(backgroundRuntime, (blob : Blob) => {
-            'worklet';
-
-            const reader = new FileReader();
-            reader.onloadend = () => resolve(reader.result as string);
-            reader.readAsDataURL(blob);
-        })(blob)
+    return new Promise<string>((resolve, reject) => {
+        BackgroundFileReader.readBlobInBackground(blob, resolve, reject)
     });
   }

ios/FileReader.swift

@@ -0,0 +1,9 @@
+@objc(BackgroundFileReader)
+class BackgroundFileReader: NSObject {
+  @objc func readBlobInBackground(_ blob: NSData, resolver: @escaping (String) -> Void, rejecter: @escaping (String) -> Void) {
+    DispatchQueue.global(qos: .background).async {
+      let base64String = blob.base64EncodedString(options: [])
+      resolver(base64String)
+    }
+  }
+}