convert orientation property value of medium to satisfy EXIF standard both on Android and iOS (on iOS, provide orientation property only when get single medium rather than list media)

android/src/main/kotlin/com/morbit/photogallery/PhotoGalleryPlugin.kt

@@ -816,7 +816,7 @@ class PhotoGalleryPlugin : FlutterPlugin, MethodCallHandler {
             "mediumType" to imageType,
             "width" to width,
             "height" to height,
-            "orientation" to orientation,
+            "orientation" to orientationDegree2Value(orientation),
             "mimeType" to mimeType,
             "creationDate" to dateTaken,
             "modifiedDate" to dateModified
@@ -852,7 +852,7 @@ class PhotoGalleryPlugin : FlutterPlugin, MethodCallHandler {
             "id" to id.toString(),
             "mediumType" to videoType,
             "width" to width,
-            "orientation" to orientation,
+            "orientation" to orientationDegree2Value(orientation),
             "height" to height,
             "mimeType" to mimeType,
             "duration" to duration,
@@ -861,6 +861,16 @@ class PhotoGalleryPlugin : FlutterPlugin, MethodCallHandler {
         )
     }
 
+    private fun orientationDegree2Value(degree: Long): Int {
+        return when (degree) {
+            0L -> 1
+            90L -> 8
+            180L -> 3
+            270L -> 6
+            else -> 0
+        }
+    }
+
     private fun getCachePath(): File? {
         return this.context?.run {
             val cachePath = File(this.cacheDir, "photo_gallery")

ios/Classes/SwiftPhotoGalleryPlugin.swift

@@ -211,13 +211,17 @@ public class SwiftPhotoGalleryPlugin: NSObject, FlutterPlugin {
     }
     let assets: PHFetchResult = PHAsset.fetchAssets(withLocalIdentifiers: [mediumId], options: fetchOptions)
     
-    if (assets.count > 0) {
+    if (assets.count <= 0) {
+      completion(nil, NSError(domain: "photo_gallery", code: 404, userInfo: nil))
+    } else {
       let asset: PHAsset = assets[0]
-      completion(getMediumFromAsset(asset: asset), nil)
+      getMediumFromAssetAsync(
-      return
+        asset: asset,
+        completion: { (data: [String: Any?]?, error: Error?) -> Void in
+          completion(data, nil)
+        }
+      )
     }
-    
-    completion(nil, NSError(domain: "photo_gallery", code: 404, userInfo: nil))
   }
   
   private func getThumbnail(
@@ -423,6 +427,28 @@ public class SwiftPhotoGalleryPlugin: NSObject, FlutterPlugin {
       "modifiedDate": (asset.modificationDate != nil) ? NSInteger(asset.modificationDate!.timeIntervalSince1970 * 1000) : nil
     ]
   }
+  
+  private func getMediumFromAssetAsync(asset: PHAsset, completion: @escaping ([String : Any?]?, Error?) -> Void) -> Void {
+    let mimeType = self.extractMimeTypeFromAsset(asset: asset)
+    let manager = PHImageManager.default()
+    manager.requestImageData(
+      for: asset,
+      options: nil,
+      resultHandler: { (data: Data?, uti: String?, orientation: UIImage.Orientation, info: ([AnyHashable: Any]?)) -> Void in
+        completion([
+          "id": asset.localIdentifier,
+          "mediumType": self.toDartMediumType(value: asset.mediaType),
+          "mimeType": mimeType,
+          "height": asset.pixelHeight,
+          "width": asset.pixelWidth,
+          "orientation": self.toOrientationValue(orientation: orientation),
+          "duration": NSInteger(asset.duration * 1000),
+          "creationDate": (asset.creationDate != nil) ? NSInteger(asset.creationDate!.timeIntervalSince1970 * 1000) : nil,
+          "modifiedDate": (asset.modificationDate != nil) ? NSInteger(asset.modificationDate!.timeIntervalSince1970 * 1000) : nil
+        ], nil)
+      }
+    )
+  }
 
   private func exportPathForAsset(asset: PHAsset, ext: String) -> URL {
     let mediumId = asset.localIdentifier
@@ -450,6 +476,29 @@ public class SwiftPhotoGalleryPlugin: NSObject, FlutterPlugin {
     }
   }
   
+  private func toOrientationValue(orientation: UIImage.Orientation) -> Int {
+    switch orientation {
+    case UIImage.Orientation.up:
+      return 1
+    case UIImage.Orientation.down:
+      return 3
+    case UIImage.Orientation.left:
+      return 6
+    case UIImage.Orientation.right:
+      return 8
+    case UIImage.Orientation.upMirrored:
+      return 2
+    case UIImage.Orientation.downMirrored:
+      return 4
+    case UIImage.Orientation.leftMirrored:
+      return 5
+    case UIImage.Orientation.rightMirrored:
+      return 7
+    @unknown default:
+      return 0
+    }
+  }
+  
   private func predicateFromMediumTypes(mediumTypes: [String]) -> NSPredicate {
     let predicates = mediumTypes.map { (dartValue) -> NSPredicate in
       return predicateFromMediumType(mediumType: dartValue)