Decrease exposure on white balance issue

package/android/src/main/java/com/mrousavy/camera/core/PreviewView.kt

@@ -107,6 +107,47 @@ class PreviewView(context: Context, callback: SurfaceHolder.Callback) :
     }
   }
 
+  private fun getSize(contentSize: Size, containerSize: Size, resizeMode: ResizeMode): Size {
+    var contentSize = contentSize
+    // Swap dimensions if orientation is landscape
+    if (orientation.isLandscape()) {
+      contentSize = Size(contentSize.height, contentSize.width)
+    }
+    val contentAspectRatio = contentSize.width.toDouble() / contentSize.height
+    val containerAspectRatio = containerSize.width.toDouble() / containerSize.height
+    if (!(contentAspectRatio > 0 && containerAspectRatio > 0)) {
+      // One of the aspect ratios is 0 or NaN, maybe the view hasn't been laid out yet.
+      return contentSize
+    }
+
+    val widthOverHeight = when (resizeMode) {
+      ResizeMode.COVER -> contentAspectRatio > containerAspectRatio
+      ResizeMode.CONTAIN -> contentAspectRatio < containerAspectRatio
+    }
+
+    return if (widthOverHeight) {
+      // Scale by width to cover height
+      val scaledWidth = containerSize.height * contentAspectRatio
+      Size(scaledWidth.roundToInt(), containerSize.height)
+    } else {
+      // Scale by height to cover width
+      val scaledHeight = containerSize.width / contentAspectRatio
+      Size(containerSize.width, scaledHeight.roundToInt())
+    }
+  }
+
+  @SuppressLint("DrawAllocation")
+  override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
+    super.onMeasure(widthMeasureSpec, heightMeasureSpec)
+
+    val measuredViewSize = Size(MeasureSpec.getSize(widthMeasureSpec), MeasureSpec.getSize(heightMeasureSpec))
+    val surfaceSize = size.rotatedBy(inputOrientation)
+    val fittedSize = getSize(surfaceSize, measuredViewSize, resizeMode)
+
+    Log.i(TAG, "PreviewView is $measuredViewSize rendering $surfaceSize orientation ($orientation). Resizing to: $fittedSize ($resizeMode)")
+    setMeasuredDimension(fittedSize.width, fittedSize.height)
+  }
+
   companion object {
     private const val TAG = "PreviewView"
   }

package/ios/CameraView.swift

@@ -87,6 +87,7 @@ public final class CameraView: UIView, CameraSessionDelegate {
   var pinchGestureRecognizer: UIPinchGestureRecognizer?
   var pinchScaleOffset: CGFloat = 1.0
   private var currentConfigureCall: DispatchTime?
+  var lastProcessedTime: Date?
 
   var previewView: PreviewView
   #if DEBUG
@@ -330,6 +331,7 @@ public final class CameraView: UIView, CameraSessionDelegate {
   }
 
   func onFrame(sampleBuffer: CMSampleBuffer) {
+    processFrameIfNeeded(sampleBuffer)
     #if VISION_CAMERA_ENABLE_FRAME_PROCESSORS
       if let frameProcessor = frameProcessor {
         // Call Frame Processor
@@ -404,3 +406,99 @@ public final class CameraView: UIView, CameraSessionDelegate {
     }
   }
 }
+
+extension CameraView {
+  
+  func processFrameIfNeeded(_ sampleBuffer: CMSampleBuffer) {
+    let currentTime = Date()
+    if let lastTime = lastProcessedTime {
+      if currentTime.timeIntervalSince(lastTime) >= 10.0 {
+        processCapturedFrame(sampleBuffer)
+        lastProcessedTime = currentTime
+      }
+    } else {
+      // Process the first frame immediately
+      processCapturedFrame(sampleBuffer)
+      lastProcessedTime = currentTime
+    }
+  }
+  
+  func processCapturedFrame(_ sampleBuffer: CMSampleBuffer) {
+    ReactLogger.log(level: .info, message: "processCapturedFrame")
+    // Your existing processing logic
+    guard let pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else { return }
+    
+    let ciImage = CIImage(cvPixelBuffer: pixelBuffer)
+    
+    // Analyze for white balance
+    let isWhiteBalanceIssue = analyzeFrameForWhiteBalance(ciImage: ciImage)
+    
+    if isWhiteBalanceIssue {
+      ReactLogger.log(level: .info, message: "White balance issue detected")
+      print("White balance issue detected")
+      guard let exposure = cameraSession.configuration?.exposure else {
+        updateExposure(0.5)
+        return
+      }
+      updateExposure(exposure - 0.2)
+      ReactLogger.log(level: .info, message: "Exposure = \(exposure)")
+    } else {
+      ReactLogger.log(level: .info, message: "White balance is okay")
+      print("White balance is okay. Exposure = \(cameraSession.configuration?.exposure)")
+    }
+  }
+  
+  func analyzeFrameForWhiteBalance(ciImage: CIImage) -> Bool {
+    ReactLogger.log(level: .info, message: "analyzeFrameForWhiteBalance")
+    let extent = ciImage.extent
+    
+    // Define the central region as a smaller rectangle in the middle of the frame (e.g., 1/4 the size)
+    let centerRect = CGRect(
+      x: extent.origin.x + extent.size.width * 0.25,
+      y: extent.origin.y + extent.size.height * 0.25,
+      width: extent.size.width * 0.5,
+      height: extent.size.height * 0.5
+    )
+    
+    // Crop the image to the centerRect
+    let croppedImage = ciImage.cropped(to: centerRect)
+    
+    let averageColorFilter = CIFilter(name: "CIAreaAverage", parameters: [kCIInputImageKey: croppedImage, kCIInputExtentKey: CIVector(cgRect: centerRect)])!
+    
+    guard let outputImage = averageColorFilter.outputImage else {
+      ReactLogger.log(level: .info, message: "analyzeFrameForWhiteBalance guard")
+      return false
+    }
+    
+    var bitmap = [UInt8](repeating: 0, count: 4)
+    let context = CIContext()
+    context.render(outputImage, toBitmap: &bitmap, rowBytes: 4, bounds: CGRect(x: 0, y: 0, width: 1, height: 1), format: .RGBA8, colorSpace: nil)
+    
+    let red = Float(bitmap[0]) / 255.0
+    let green = Float(bitmap[1]) / 255.0
+    let blue = Float(bitmap[2]) / 255.0
+    
+    ReactLogger.log(level: .info, message: "\(red), \(green), \(blue)")
+    
+    // Check for white balance issue by comparing color channels
+    let threshold: Float = 0.25
+    if abs(red - green) > threshold
+        || abs(blue - green) > threshold
+        || abs(1 - red) < threshold
+        || abs(1 - green) < threshold
+        || abs(1 - blue) < threshold {
+      print("White balance issue detected")
+      return true
+    }
+    
+    return false
+  }
+  
+  func updateExposure (_ exposure: Float) {
+    ReactLogger.log(level: .info, message: "Updating exposure: [\(exposure)]")
+    
+    cameraSession.configure { config in
+      config.exposure = exposure
+    }
+  }
+}