feat: Implement exposure (#2173)

* feat: Implement `exposure` (iOS)

* Update Podfile.lock

* Format

* Expose exposure in format

* Set exposure in Camera2

* fix: Fix exposure calculation

* Add exposure docs

package/ios/CameraView.swift

@@ -46,6 +46,7 @@ public final class CameraView: UIView, CameraSessionDelegate {
   @objc var isActive = false
   @objc var torch = "off"
   @objc var zoom: NSNumber = 1.0 // in "factor"
+  @objc var exposure: NSNumber = 1.0
   @objc var enableFpsGraph = false
   @objc var videoStabilizationMode: NSString?
   @objc var resizeMode: NSString = "cover" {
@@ -218,6 +219,9 @@ public final class CameraView: UIView, CameraSessionDelegate {
       // Zoom
       config.zoom = zoom.doubleValue
 
+      // Exposure
+      config.exposure = exposure.floatValue
+
       // isActive
       config.isActive = isActive
     }

package/ios/CameraViewManager.m

@@ -44,6 +44,7 @@ RCT_EXPORT_VIEW_PROPERTY(pixelFormat, NSString);
 // other props
 RCT_EXPORT_VIEW_PROPERTY(torch, NSString);
 RCT_EXPORT_VIEW_PROPERTY(zoom, NSNumber);
+RCT_EXPORT_VIEW_PROPERTY(exposure, NSNumber);
 RCT_EXPORT_VIEW_PROPERTY(enableZoomGesture, BOOL);
 RCT_EXPORT_VIEW_PROPERTY(enableFpsGraph, BOOL);
 RCT_EXPORT_VIEW_PROPERTY(orientation, NSString);

package/ios/Core/CameraConfiguration.swift

@@ -39,6 +39,9 @@ class CameraConfiguration {
   // Zoom
   var zoom: CGFloat?
 
+  // Exposure
+  var exposure: Float?
+
   // isActive (Start/Stop)
   var isActive = false
 
@@ -59,6 +62,7 @@ class CameraConfiguration {
       enableLowLightBoost = other.enableLowLightBoost
       torch = other.torch
       zoom = other.zoom
+      exposure = other.exposure
       isActive = other.isActive
       audio = other.audio
     } else {
@@ -77,6 +81,7 @@ class CameraConfiguration {
     let sidePropsChanged: Bool
     let torchChanged: Bool
     let zoomChanged: Bool
+    let exposureChanged: Bool
 
     let audioSessionChanged: Bool
 
@@ -113,6 +118,8 @@ class CameraConfiguration {
       torchChanged = left?.isActive != right.isActive || left?.torch != right.torch
       // zoom (depends on format)
       zoomChanged = formatChanged || left?.zoom != right.zoom
+      // exposure (depends on format)
+      exposureChanged = formatChanged || left?.exposure != right.exposure
 
       // audio session
       audioSessionChanged = left?.audio != right.audio

package/ios/Core/CameraSession+Configuration.swift

@@ -285,6 +285,20 @@ extension CameraSession {
     device.videoZoomFactor = clamped
   }
 
+  // pragma MARK: Exposure
+
+  /**
+   Configures exposure (`exposure`) as a bias that adjusts exposureTime and ISO.
+   */
+  func configureExposure(configuration: CameraConfiguration, device: AVCaptureDevice) {
+    guard let exposure = configuration.exposure else {
+      return
+    }
+
+    let clamped = max(min(exposure, device.maxExposureTargetBias), device.minExposureTargetBias)
+    device.setExposureTargetBias(clamped)
+  }
+
   // pragma MARK: Audio
 
   /**

package/ios/Core/CameraSession.swift

@@ -154,13 +154,17 @@ class CameraSession: NSObject, AVCaptureVideoDataOutputSampleBufferDelegate, AVC
             if difference.zoomChanged {
               self.configureZoom(configuration: config, device: device)
             }
+            // 8. Configure exposure bias
+            if difference.exposureChanged {
+              self.configureExposure(configuration: config, device: device)
+            }
           }
         }
 
-        // 8. Start or stop the session if needed
+        // 9. Start or stop the session if needed
         self.checkIsActive(configuration: config)
 
-        // 9. Enable or disable the Torch if needed (requires session to be running)
+        // 10. Enable or disable the Torch if needed (requires session to be running)
         if difference.torchChanged {
           try self.withDeviceLock { device in
             try self.configureTorch(configuration: config, device: device)