feat: ✨ Improve error handling (#9)

-Added check to avoid producing images with large size
-Use CIContext for proper image conversion process to avoid crashes on some devices

packages/react-native-background-remover/ios/ReactNativeBackgroundRemover.swift

@@ -4,49 +4,74 @@ import CoreImage
 public class BackgroundRemoverSwift: NSObject {
 
     @objc
-    public func removeBackground(_ imageURI: String, resolve: @escaping RCTPromiseResolveBlock, reject: @escaping RCTPromiseRejectBlock)->Void {
+    public func removeBackground(_ imageURI: String, resolve: @escaping RCTPromiseResolveBlock, reject: @escaping RCTPromiseRejectBlock) -> Void {
         #if targetEnvironment(simulator)
         reject("BackgroundRemover", "SimulatorError", NSError(domain: "BackgroundRemover", code: 2))
-            return
+        return
         #endif
 
         if #available(iOS 15.0, *) {
-            let url = URL(string: imageURI)!
-            let originalImage = CIImage(contentsOf: url, options: [.applyOrientationProperty: true])!
+            guard let url = URL(string: imageURI) else {
+                reject("BackgroundRemover", "Invalid URL", NSError(domain: "BackgroundRemover", code: 3))
+                return
+            }
+
+            guard let originalImage = CIImage(contentsOf: url, options: [.applyOrientationProperty: true]) else {
+                reject("BackgroundRemover", "Unable to load image", NSError(domain: "BackgroundRemover", code: 4))
+                return
+            }
+
             let imageRequestHandler = VNImageRequestHandler(ciImage: originalImage)
 
             var segmentationRequest = VNGeneratePersonSegmentationRequest()
-            segmentationRequest = VNGeneratePersonSegmentationRequest()
             segmentationRequest.qualityLevel = .accurate
             segmentationRequest.outputPixelFormat = kCVPixelFormatType_OneComponent8
 
             DispatchQueue.global(qos: .userInitiated).async {
                 do {
                     try imageRequestHandler.perform([segmentationRequest])
-                    let pixelBuffer =  segmentationRequest.results?.first!.pixelBuffer
+                    guard let pixelBuffer = segmentationRequest.results?.first?.pixelBuffer else {
+                        reject("BackgroundRemover", "No segmentation results", NSError(domain: "BackgroundRemover", code: 5))
+                        return
+                    }
 
-                    var maskImage = CIImage(cvPixelBuffer: pixelBuffer!)
+                    var maskImage = CIImage(cvPixelBuffer: pixelBuffer)
 
+                    // Adjust mask scaling
                     let scaleX = originalImage.extent.width / maskImage.extent.width
                     let scaleY = originalImage.extent.height / maskImage.extent.height
-                    maskImage = maskImage.transformed(by: .init(scaleX: scaleX, y: scaleY))
+
+                    // Avoid up-scaling if mask dimensions are too small
+                    if scaleX > 1 || scaleY > 1 {
+                        maskImage = maskImage.transformed(by: CGAffineTransform(scaleX: scaleX, y: scaleY))
+                    }
 
                     let maskedImage = originalImage.applyingFilter("CIBlendWithMask", parameters: [kCIInputMaskImageKey: maskImage])
 
-                    // Save the masked image to a temporary file
-                    let tempURL = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent(url.lastPathComponent)
-                    let uiImage = UIImage(ciImage: maskedImage)
-                    if let data = uiImage.pngData() {
+                    // Convert to UIImage via CGImage for better control
+                    let context = CIContext()
+                    guard let cgMaskedImage = context.createCGImage(maskedImage, from: maskedImage.extent) else {
+                        reject("BackgroundRemover", "Error creating CGImage", NSError(domain: "BackgroundRemover", code: 6))
+                        return
+                    }
+
+                    let uiImage = UIImage(cgImage: cgMaskedImage)
+
+                    // Save the image as PNG to preserve transparency
+                    let tempURL = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent(url.lastPathComponent).appendingPathExtension("png")
+                    if let data = uiImage.pngData() { // Use PNG to preserve transparency
                         try data.write(to: tempURL)
                         resolve(tempURL.absoluteString)
+                    } else {
+                        reject("BackgroundRemover", "Error saving image", NSError(domain: "BackgroundRemover", code: 7))
                     }
+
                 } catch {
-                    reject("BackgroundRemover", "[ReactNativeBackgroundRemover]: Error removing background", error)
+                    reject("BackgroundRemover", "Error removing background", error)
                 }
             }
         } else {
-            reject("BackgroundRemover", "[ReactNativeBackgroundRemover]: You need to have a device with at least iOS 15", NSError(domain: "BackgroundRemover", code: 1))
-            return
+            reject("BackgroundRemover", "You need a device with iOS 15 or later", NSError(domain: "BackgroundRemover", code: 1))
         }
     }
 }