fix iOS

flutter_filament/ios/Classes/FlutterFilamentTexture.swift

@@ -0,0 +1,48 @@
+import Foundation
+import GLKit
+import Flutter
+
+public class FlutterFilamentTexture : NSObject, FlutterTexture {
+    
+    public var pixelBuffer: CVPixelBuffer?
+    
+    var pixelBufferAttrs = [
+        kCVPixelBufferPixelFormatTypeKey: NSNumber(value: kCVPixelFormatType_32BGRA),
+        kCVPixelBufferOpenGLCompatibilityKey: kCFBooleanTrue,
+        kCVPixelBufferOpenGLESCompatibilityKey: kCFBooleanTrue,
+        kCVPixelBufferIOSurfacePropertiesKey: [:]
+    ] as CFDictionary
+
+    var flutterTextureId: Int64 = -1
+    var registry: FlutterTextureRegistry?
+    
+    init(width:Int64, height:Int64, registry:FlutterTextureRegistry) {
+        self.registry = registry
+
+        super.init()
+        
+        if(CVPixelBufferCreate(kCFAllocatorDefault, Int(width), Int(height),
+                               kCVPixelFormatType_32BGRA, pixelBufferAttrs, &pixelBuffer) != kCVReturnSuccess) {
+            print("Error allocating pixel buffer")
+        } else { 
+            self.flutterTextureId = registry.register(self)
+        }
+    }
+        
+    public func copyPixelBuffer() -> Unmanaged<CVPixelBuffer>? {
+        return Unmanaged.passRetained(pixelBuffer!);
+    }
+    
+    public func onTextureUnregistered(_ texture:FlutterTexture) {
+        print("Texture unregistered")
+    }
+    
+    public func destroy() {
+        if(self.flutterTextureId != -1) {
+            self.registry!.unregisterTexture(self.flutterTextureId)
+        }
+
+        self.pixelBuffer = nil
+    }
+    
+}