feat: Add mirrorHorizontally() (#99)

* feat: Add `mirrorHorizontally()`

* Update README.md

Author: mrousavy

README.md

@@ -174,6 +174,15 @@ const webImage   = await WebImages.loadFromURLAsync('https://picsum.photos/seed/
 const upsideDown = await webImage.rotateAsync(180)
 ```
 
+#### Mirroring
+
+An `Image` can be mirrored horizontally (left <-> right) entirely in-memory, without ever writing to- or reading from- a file:
+
+```ts
+const webImage = await WebImages.loadFromURLAsync('https://picsum.photos/seed/123/400')
+const mirrored = await webImage.mirrorHorizontallyAsync()
+```
+
 #### Render into another Image
 
 An `Image` can be rendered into another `Image` entirely in-memory. This creates a third image (the result):

bun.lock

@@ -2493,9 +2493,9 @@ DEPENDENCIES:
   - fmt (from `../../node_modules/react-native/third-party-podspecs/fmt.podspec`)
   - glog (from `../../node_modules/react-native/third-party-podspecs/glog.podspec`)
   - hermes-engine (from `../../node_modules/react-native/sdks/hermes-engine/hermes-engine.podspec`)
-  - NitroImage (from `../node_modules/react-native-nitro-image`)
+  - NitroImage (from `../../node_modules/react-native-nitro-image`)
   - NitroModules (from `../../node_modules/react-native-nitro-modules`)
-  - NitroWebImage (from `../node_modules/react-native-nitro-web-image`)
+  - NitroWebImage (from `../../node_modules/react-native-nitro-web-image`)
   - RCT-Folly (from `../../node_modules/react-native/third-party-podspecs/RCT-Folly.podspec`)
   - RCTDeprecation (from `../../node_modules/react-native/ReactApple/Libraries/RCTFoundation/RCTDeprecation`)
   - RCTRequired (from `../../node_modules/react-native/Libraries/Required`)
@@ -2591,11 +2591,11 @@ EXTERNAL SOURCES:
     :podspec: "../../node_modules/react-native/sdks/hermes-engine/hermes-engine.podspec"
     :tag: hermes-2025-07-07-RNv0.81.0-e0fc67142ec0763c6b6153ca2bf96df815539782
   NitroImage:
-    :path: "../node_modules/react-native-nitro-image"
+    :path: "../../node_modules/react-native-nitro-image"
   NitroModules:
     :path: "../../node_modules/react-native-nitro-modules"
   NitroWebImage:
-    :path: "../node_modules/react-native-nitro-web-image"
+    :path: "../../node_modules/react-native-nitro-web-image"
   RCT-Folly:
     :podspec: "../../node_modules/react-native/third-party-podspecs/RCT-Folly.podspec"
   RCTDeprecation:

example/ios/Podfile.lock

@@ -16,8 +16,8 @@
     "react": "19.1.0",
     "react-native": "0.81.0",
     "react-native-fast-image": "^8.6.3",
-    "react-native-nitro-image": "../packages/react-native-nitro-image",
-    "react-native-nitro-web-image": "../packages/react-native-nitro-web-image",
+    "react-native-nitro-image": "workspace:*",
+    "react-native-nitro-web-image": "workspace:*",
     "react-native-nitro-modules": "0.33.9",
     "react-native-safe-area-context": "^5.6.0",
     "react-native-screens": "^4.14.1"

example/package.json

@@ -1,6 +1,5 @@
 {
   "name": "react-native-nitro-image-monorepo",
-  "packageManager": "bun@1.3.9",
   "private": true,
   "version": "0.11.1",
   "repository": "https://github.com/mrousavy/react-native-nitro-image.git",

package.json

@@ -134,6 +134,18 @@ class HybridImage: HybridImageSpec {
         return Promise.async { crop(startX, startY, endX, endY) }
     }
 
+    override fun mirrorHorizontally(): HybridImageSpec {
+        val matrix = Matrix().apply {
+            preScale(-1f, 1f)
+        }
+        val mirrored = Bitmap.createBitmap(bitmap, 0, 0, bitmap.width, bitmap.height, matrix, false)
+        return HybridImage(mirrored)
+    }
+
+    override fun mirrorHorizontallyAsync(): Promise<HybridImageSpec> {
+        return Promise.async { mirrorHorizontally() }
+    }
+
     override fun saveToFileAsync(
         path: String,
         format: ImageFormat,

packages/react-native-nitro-image/android/src/main/java/com/margelo/nitro/image/HybridImage.kt

@@ -36,7 +36,7 @@ public extension NativeImage {
   func toRawPixelData(allowGpu _: Bool?) throws -> RawPixelData {
     return try uiImage.toRawPixelData()
   }
-  func toRawPixelDataAsync(allowGpu: Bool?) throws -> Promise<RawPixelData> {
+  func toRawPixelDataAsync(allowGpu: Bool?) -> Promise<RawPixelData> {
     return Promise.async {
       return try self.toRawPixelData(allowGpu: allowGpu)
     }
@@ -46,12 +46,12 @@ public extension NativeImage {
     return try uiImage.toEncodedImageData(format: format, quality: quality ?? 100)
   }
 
-  func toEncodedImageDataAsync(format: ImageFormat, quality: Double?) throws -> Promise<EncodedImageData> {
+  func toEncodedImageDataAsync(format: ImageFormat, quality: Double?) -> Promise<EncodedImageData> {
     return Promise.async {
       return try self.toEncodedImageData(format: format, quality: quality)
     }
   }
-  
+
   func rotate(degrees: Double, allowFastFlagRotation: Bool?) -> any HybridImageSpec {
     if allowFastFlagRotation == true,
        degrees.truncatingRemainder(dividingBy: 90) == 0,
@@ -105,7 +105,7 @@ public extension NativeImage {
     return HybridImage(uiImage: resizedImage)
   }
 
-  func resizeAsync(width: Double, height: Double) throws -> Promise<any HybridImageSpec> {
+  func resizeAsync(width: Double, height: Double) -> Promise<any HybridImageSpec> {
     return Promise.async {
       return try self.resize(width: width, height: height)
     }
@@ -133,12 +133,23 @@ public extension NativeImage {
     return HybridImage(uiImage: croppedUiImage)
   }
 
-  func cropAsync(startX: Double, startY: Double, endX: Double, endY: Double) throws -> Promise<any HybridImageSpec> {
+  func cropAsync(startX: Double, startY: Double, endX: Double, endY: Double) -> Promise<any HybridImageSpec> {
     return Promise.async {
       return try self.crop(startX: startX, startY: startY, endX: endX, endY: endY)
     }
   }
 
+  func mirrorHorizontally() -> any HybridImageSpec {
+    let mirrored = uiImage.withHorizontallyFlippedOrientation()
+    return HybridImage(uiImage: mirrored)
+  }
+
+  func mirrorHorizontallyAsync() -> Promise<any HybridImageSpec> {
+    return Promise.async {
+      return mirrorHorizontally()
+    }
+  }
+
   private func saveImage(to path: String, format: ImageFormat, quality: Double) throws {
     let data = try uiImage.getData(in: format, quality: quality)
     guard let url = URL(string: path) else {
@@ -147,13 +158,13 @@ public extension NativeImage {
     try data.write(to: url)
   }
 
-  func saveToFileAsync(path: String, format: ImageFormat, quality: Double?) throws -> Promise<Void> {
+  func saveToFileAsync(path: String, format: ImageFormat, quality: Double?) -> Promise<Void> {
     return Promise.async(.utility) {
       try self.saveImage(to: path, format: format, quality: quality ?? 100.0)
     }
   }
 
-  func saveToTemporaryFileAsync(format: ImageFormat, quality: Double?) throws -> Promise<String> {
+  func saveToTemporaryFileAsync(format: ImageFormat, quality: Double?) -> Promise<String> {
     return Promise.async(.utility) {
       let tempDirectory = FileManager.default.temporaryDirectory
       let fileName = UUID().uuidString
@@ -170,12 +181,12 @@ public extension NativeImage {
     return try ArrayBuffer.copy(data: thumbHash)
   }
 
-  func toThumbHashAsync() throws -> Promise<ArrayBuffer> {
+  func toThumbHashAsync() -> Promise<ArrayBuffer> {
     return Promise.async {
       return try self.toThumbHash()
     }
   }
-  
+
   func renderInto(image newImage: any HybridImageSpec, x: Double, y: Double, width: Double, height: Double) throws -> any HybridImageSpec {
     guard let newImage = newImage as? NativeImage else {
       throw RuntimeError.error(withMessage: "The given image (\(newImage)) is not a `NativeImage`!")
@@ -186,16 +197,16 @@ public extension NativeImage {
     let renderedImage = renderer.image { context in
       // 2. Render our own image (copy)
       self.uiImage.draw(at: .zero)
-      
+
       // 3. Render the new image into our copy
       let rect = CGRect(x: x, y: y, width: width, height: height)
       newImage.uiImage.draw(in: rect)
     }
     // 4. Wrap the resulting UIImage in a HybridImage
     return HybridImage(uiImage: renderedImage)
   }
-  
-  func renderIntoAsync(image newImage: any HybridImageSpec, x: Double, y: Double, width: Double, height: Double) throws -> Promise<any HybridImageSpec> {
+
+  func renderIntoAsync(image newImage: any HybridImageSpec, x: Double, y: Double, width: Double, height: Double) -> Promise<any HybridImageSpec> {
     return Promise.async {
       return try self.renderInto(image: newImage, x: x, y: y, width: width, height: height)
     }