feat: add exposure compensation for camera preview

camposer/src/androidTest/java/com/ujizin/camposer/ExposureCompensationTest.kt

@@ -0,0 +1,70 @@
+package com.ujizin.camposer
+
+import androidx.compose.runtime.MutableState
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.ui.test.junit4.ComposeContentTestRule
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import androidx.test.filters.LargeTest
+import junit.framework.TestCase.assertEquals
+import org.junit.Assert.assertNotEquals
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@RunWith(AndroidJUnit4::class)
+@LargeTest
+internal class ExposureCompensationTest: CameraTest() {
+
+    private lateinit var exposureCompensation: MutableState<Int>
+
+    private val currentExposure: Int?
+        get() = cameraState.controller.cameraInfo?.exposureState?.exposureCompensationIndex
+
+    @Test
+    fun test_minExposureCompensation() = with(composeTestRule) {
+        initCameraWithExposure(0)
+
+        exposureCompensation.value = cameraState.minExposure
+
+        runOnIdle {
+            assertEquals(cameraState.minExposure, currentExposure)
+            assertEquals(exposureCompensation.value, currentExposure)
+        }
+    }
+
+    @Test
+    fun test_maxExposureCompensation() = with(composeTestRule) {
+        initCameraWithExposure(0)
+
+        exposureCompensation.value = cameraState.maxExposure
+
+        runOnIdle {
+            assertEquals(cameraState.maxExposure, currentExposure)
+            assertEquals(exposureCompensation.value, currentExposure)
+        }
+    }
+
+
+    @Test
+    fun test_invalidExposureCompensation() = with(composeTestRule) {
+        initCameraWithExposure(0)
+
+        exposureCompensation.value = Int.MAX_VALUE
+
+        runOnIdle {
+            assertNotEquals(cameraState.maxExposure, currentExposure)
+            assertNotEquals(exposureCompensation.value, currentExposure)
+            assertEquals(cameraState.initialExposure, currentExposure)
+        }
+    }
+
+    private fun ComposeContentTestRule.initCameraWithExposure(
+        exposure: Int,
+    ) = initCameraState { state ->
+        exposureCompensation = remember { mutableStateOf(exposure) }
+        CameraPreview(
+            cameraState = state,
+            exposureCompensation = exposureCompensation.value
+        )
+    }
+}

camposer/src/main/java/com/ujizin/camposer/CameraPreview.kt

@@ -44,6 +44,7 @@ import androidx.camera.core.CameraSelector as CameraXSelector
  * @param flashMode flash mode to be added, default is off
  * @param scaleType scale type to be added, default is fill center
  * @param enableTorch enable torch from camera, default is false.
+ * @param exposureCompensation camera exposure compensation to be added
  * @param zoomRatio zoom ratio to be added, default is 1.0
  * @param imageAnalyzer image analyzer from camera, see [ImageAnalyzer]
  * @param implementationMode implementation mode to be added, default is performance
@@ -71,6 +72,7 @@ public fun CameraPreview(
     flashMode: FlashMode = cameraState.flashMode,
     scaleType: ScaleType = cameraState.scaleType,
     enableTorch: Boolean = cameraState.enableTorch,
+    exposureCompensation: Int = cameraState.initialExposure,
     zoomRatio: Float = 1F,
     imageAnalyzer: ImageAnalyzer? = null,
     implementationMode: ImplementationMode = cameraState.implementationMode,
@@ -93,6 +95,7 @@ public fun CameraPreview(
         cameraState = cameraState,
         camSelector = camSelector,
         captureMode = captureMode,
+        exposureCompensation = exposureCompensation,
         imageCaptureMode = imageCaptureMode,
         imageCaptureTargetSize = imageCaptureTargetSize,
         flashMode = flashMode,
@@ -129,6 +132,7 @@ internal fun CameraPreviewImpl(
     zoomRatio: Float,
     implementationMode: ImplementationMode,
     imageAnalyzer: ImageAnalyzer?,
+    exposureCompensation: Int,
     isImageAnalysisEnabled: Boolean,
     isFocusOnTapEnabled: Boolean,
     isPinchToZoomEnabled: Boolean,
@@ -198,7 +202,8 @@ internal fun CameraPreviewImpl(
                     enableTorch = enableTorch,
                     zoomRatio = zoomRatio,
                     imageCaptureMode = imageCaptureMode,
-                    meteringPoint = meteringPointFactory.createPoint(x, y)
+                    meteringPoint = meteringPointFactory.createPoint(x, y),
+                    exposureCompensation = exposureCompensation,
                 )
             }
 

camposer/src/main/java/com/ujizin/camposer/state/CameraState.kt

@@ -75,6 +75,37 @@ public class CameraState internal constructor(context: Context) {
     )
         internal set
 
+
+    /**
+     * Get range compensation range from camera.
+     * */
+    private val exposureCompensationRange
+        get() = controller.cameraInfo?.exposureState?.exposureCompensationRange
+
+    /**
+     * Get min exposure from camera.
+     * */
+    public var minExposure: Int by mutableStateOf(
+        exposureCompensationRange?.lower ?: INITIAL_EXPOSURE_VALUE
+    )
+        internal set
+
+    /**
+     * Get max exposure from camera.
+     * */
+    public var maxExposure: Int by mutableStateOf(
+        exposureCompensationRange?.upper ?: INITIAL_EXPOSURE_VALUE
+    )
+        internal set
+
+    public val initialExposure: Int = INITIAL_EXPOSURE_VALUE
+        get() = controller.cameraInfo?.exposureState?.exposureCompensationIndex ?: field
+
+    /**
+     * Check if compensation exposure is supported.
+     * */
+    public val isExposureSupported: Boolean by derivedStateOf { maxExposure != INITIAL_EXPOSURE_VALUE }
+
     /**
      * Check if camera is streaming or not.
      * */
@@ -282,11 +313,16 @@ public class CameraState internal constructor(context: Context) {
 
     init {
         controller.initializationFuture.addListener({
-            startZoom()
+            resetCamera()
             isInitialized = true
         }, mainExecutor)
     }
 
+    private fun startExposure() {
+        minExposure = exposureCompensationRange?.lower ?: INITIAL_EXPOSURE_VALUE
+        maxExposure = exposureCompensationRange?.upper ?: INITIAL_EXPOSURE_VALUE
+    }
+
     /**
      *  Take a picture with the camera.
      *
@@ -352,6 +388,10 @@ public class CameraState internal constructor(context: Context) {
         controller.setZoomRatio(zoomRatio.coerceIn(minZoom, maxZoom))
     }
 
+    private fun setExposureCompensation(exposureCompensation: Int) {
+        controller.cameraControl?.setExposureCompensationIndex(exposureCompensation)
+    }
+
     /**
      * Start recording camera.
      *
@@ -489,6 +529,7 @@ public class CameraState internal constructor(context: Context) {
     private fun resetCamera() {
         hasFlashUnit = controller.cameraInfo?.hasFlashUnit() ?: false
         startZoom()
+        startExposure()
     }
 
     private fun Set<Int>.sumOr(initial: Int = 0): Int = fold(initial) { acc, current ->
@@ -511,7 +552,8 @@ public class CameraState internal constructor(context: Context) {
         zoomRatio: Float,
         imageCaptureMode: ImageCaptureMode,
         enableTorch: Boolean,
-        meteringPoint: MeteringPoint
+        meteringPoint: MeteringPoint,
+        exposureCompensation: Int
     ) {
         this.camSelector = camSelector
         this.captureMode = captureMode
@@ -525,12 +567,14 @@ public class CameraState internal constructor(context: Context) {
         this.enableTorch = enableTorch
         this.isFocusOnTapSupported = meteringPoint.isFocusMeteringSupported
         this.imageCaptureMode = imageCaptureMode
+        setExposureCompensation(exposureCompensation)
         setZoomRatio(zoomRatio)
     }
 
     private companion object {
         private val TAG = this::class.java.name
         private const val INITIAL_ZOOM_VALUE = 1F
+        private const val INITIAL_EXPOSURE_VALUE = 0
     }
 }