diff --git a/android/src/main/java/io/twentysixty/rn/eidreader/EIdReaderModule.kt b/android/src/main/java/io/twentysixty/rn/eidreader/EIdReaderModule.kt
index 6795fdc..183a261 100644
--- a/android/src/main/java/io/twentysixty/rn/eidreader/EIdReaderModule.kt
+++ b/android/src/main/java/io/twentysixty/rn/eidreader/EIdReaderModule.kt
@@ -285,22 +285,19 @@ class EIdReaderModule(reactContext: ReactApplicationContext) :
     }
   }
 
-  @ReactMethod
-  fun imageDataUrlToJpegDataUrl(dataUrl:String, promise: Promise){
+  @ReactMethod(isBlockingSynchronousMethod = true)
+  fun imageDataUrlToJpegDataUrl(dataUrl:String): String {
     try {
       val dataSplit = dataUrl.split(";base64,")
       if(dataSplit.size != 2){
-        promise.reject("Cannot imageDataUrlToJpegDataUrl image because is not a valid dataurl")
-        return
+        throw Error("Cannot imageDataUrlToJpegDataUrl image because is not a valid dataurl")
       }
       val mimeType = dataSplit[0].split(":")[1]
       if(!mimeType.startsWith("image/")){
-        promise.reject("Couldn't convert $mimeType to JPEG")
-        return
+        throw Error("Couldn't convert $mimeType to JPEG")
       }
       if(mimeType == "image/jpeg"){
-        promise.resolve(dataUrl)
-        return
+        return dataUrl
       }
       val dataContent = dataSplit[1]
       val bitmapUtil = BitmapUtil(reactApplicationContext)
@@ -310,14 +307,12 @@ class EIdReaderModule(reactContext: ReactApplicationContext) :
         val byteArrayOutputStream = ByteArrayOutputStream()
         nfcImage.bitmap!!.compress(Bitmap.CompressFormat.JPEG, 70, byteArrayOutputStream)
         val bytes = byteArrayOutputStream.toByteArray()
-        promise.resolve("data:image/jpeg;base64,"+ Base64.encodeToString(bytes, Base64.CRLF))
-        return 
+        return "data:image/jpeg;base64,"+ Base64.encodeToString(bytes, Base64.CRLF)
       }
-      else promise.reject("Cannot imageDataUrlToJpegDataUrl image")
+      else throw Error("Cannot imageDataUrlToJpegDataUrl image")
   
     } catch (e: IOException) {
-      promise.reject("Cannot imageDataUrlToJpegDataUrl image")
-      return
+      throw Error("Cannot imageDataUrlToJpegDataUrl image")
     }
   }
 
diff --git a/example/src/App.tsx b/example/src/App.tsx
index 65fa98e..30fa39b 100644
--- a/example/src/App.tsx
+++ b/example/src/App.tsx
@@ -15,9 +15,13 @@ import { lena } from './data';
 
 export default function App() {
   const [result, setResult] = React.useState<EIdReadResult>();
-  const [convertedImage, setConvertedImage] = React.useState<
-    string | undefined
-  >(undefined);
+
+  let convertedImage;
+  try {
+    convertedImage = EIdReader.imageDataUrlToJpegDataUrl(lena);
+  } catch (error) {
+    console.error(error);
+  }
 
   React.useEffect(() => {
     EIdReader.addOnTagDiscoveredListener(() => {
@@ -54,16 +58,6 @@ export default function App() {
       });
   };
 
-  const imageDataUrlToJpegDataUrl = () => {
-    EIdReader.imageDataUrlToJpegDataUrl(lena)
-      .then((data) => {
-        setConvertedImage(`${data}`);
-      })
-      .catch((error) => {
-        console.error('error', error);
-      });
-  };
-
   const stopReading = () => {
     EIdReader.stopReading();
   };
@@ -100,12 +94,6 @@ export default function App() {
       <ScrollView style={styles.container}>
         <View style={styles.box}>
           <View style={styles.buttonContainer}>
-            <TouchableOpacity
-              onPress={imageDataUrlToJpegDataUrl}
-              style={styles.button}
-            >
-              <Text style={styles.buttonText}>Convert</Text>
-            </TouchableOpacity>
             <TouchableOpacity onPress={startReading} style={styles.button}>
               <Text style={styles.buttonText}>Start Reading</Text>
             </TouchableOpacity>
diff --git a/ios/EidReader.mm b/ios/EidReader.mm
index e6e8a87..688cf09 100644
--- a/ios/EidReader.mm
+++ b/ios/EidReader.mm
@@ -20,9 +20,7 @@ @interface RCT_EXTERN_MODULE(EIdReader, RCTEventEmitter)
 
 RCT_EXTERN__BLOCKING_SYNCHRONOUS_METHOD(stopReading);
 
-RCT_EXTERN_METHOD(imageDataUrlToJpegDataUrl:(NSString)dataUrl
-                  withResolver:(RCTPromiseResolveBlock)resolve
-                  withRejecter:(RCTPromiseRejectBlock)reject);
+RCT_EXTERN__BLOCKING_SYNCHRONOUS_METHOD(imageDataUrlToJpegDataUrl:(NSString)dataUrl);
 
 + (BOOL)requiresMainQueueSetup
 {
diff --git a/ios/EidReader.swift b/ios/EidReader.swift
index 8efe074..842bf7a 100644
--- a/ios/EidReader.swift
+++ b/ios/EidReader.swift
@@ -92,36 +92,34 @@ class EIdReader: RCTEventEmitter {
     }
     
   }
+    
+    enum EidReaderError: Error {
+      case invalidInput(String)
+      case processingError(String)
+    }
 
- @objc(imageDataUrlToJpegDataUrl:withResolver:withRejecter:)
-  func imageDataUrlToJpegDataUrl(
-    dataUrl: NSString,
-    resolve: @escaping RCTPromiseResolveBlock,
-    reject: @escaping RCTPromiseRejectBlock
-  ) {
+    @objc(imageDataUrlToJpegDataUrl:withError:)
+    func imageDataUrlToJpegDataUrl(dataUrl: NSString) throws -> String {
     let dataSplit = (dataUrl as String).components(separatedBy: ";base64,")
     if(dataSplit.count != 2){
-        reject("@ConvertError", "Cannot imageDataUrlToJpegDataUrl image because is not a valid dataurl", nil)
-        return
+        throw EidReaderError.invalidInput("Cannot imageDataUrlToJpegDataUrl image because is not a valid dataurl")
     }
     if let mimeType = dataSplit.first?.replacingOccurrences(of: "data:", with: ""){
         if(!mimeType.hasPrefix("image/")){
-            reject("@ConvertError", "Couldn't convert \(mimeType) to JPEG", nil)
-            return
+            throw EidReaderError.invalidInput("Couldn't convert \(mimeType) to JPEG")
         }
         if(mimeType == "image/jpeg"){
-            resolve(dataUrl)
-            return
+            return dataUrl as String
         }
         let dataContent = dataSplit[1]
         if let newData = Data(base64Encoded: dataContent) {
             if let jpegData = UIImage(data: newData)?.jpegData(compressionQuality: 1.0)?.base64EncodedString(){
-                resolve("data:image/jpeg;base64,\(jpegData)")
-                return
+                return "data:image/jpeg;base64,\(jpegData)"
+                
             }
         }
     }
-    reject("@ConvertError", "Convert image data URL to JPEG image data url error", nil)
+    throw EidReaderError.processingError("Convert image data URL to JPEG image data url error")
   }
 
   @objc(stopReading)
diff --git a/src/index.tsx b/src/index.tsx
index 46e241e..3e74d28 100644
--- a/src/index.tsx
+++ b/src/index.tsx
@@ -81,7 +81,7 @@ export default class EIdReader {
     return EIdReaderNativeModule.openNfcSettings();
   }
 
-  static imageDataUrlToJpegDataUrl(dataUrl: string): Promise<string> {
+  static imageDataUrlToJpegDataUrl(dataUrl: string): string {
     return EIdReaderNativeModule.imageDataUrlToJpegDataUrl(dataUrl);
   }