fix: Represent neutralZoom in factor instead of percentage (#179)

* Use factor instead of percent for `neutralZoom`

* fix zoom calculation

* Update CameraPage.tsx

android/src/main/java/com/mrousavy/camera/CameraViewModule.kt

@@ -173,7 +173,7 @@ class CameraViewModule(reactContext: ReactApplicationContext) : ReactContextBase
             map.putDouble("minZoom", 1.0)
             map.putDouble("maxZoom", maxScalerZoom.toDouble())
           }
-          map.putDouble("neutralZoom", characteristics.neutralZoomPercent.toDouble())
+          map.putDouble("neutralZoom", 1.0)
 
           // TODO: Optimize?
           val maxImageOutputSize = cameraConfig.outputFormats

android/src/main/java/com/mrousavy/camera/utils/CameraCharacteristicsUtils.kt

@@ -56,25 +56,3 @@ fun CameraCharacteristics.getFieldOfView(): Double {
 
   return 2 * atan(sensorSize.bigger / (focalLengths[0] * 2)) * (180 / PI)
 }
-
-fun CameraCharacteristics.supportsFps(fps: Int): Boolean {
-  return this.get(CameraCharacteristics.CONTROL_AE_AVAILABLE_TARGET_FPS_RANGES)!!
-    .any { it.upper >= fps && it.lower <= fps }
-}
-
-/**
- * Get the value at which the Zoom is at neutral state (wide-angle camera zoom 0) (in percent, between 0.0-1.0)
- *
- * * On single-camera physical devices this value will always be 0
- * * On devices with multiple cameras, e.g. triple-camera, this value will be a value between 0.0 and 1.0, where the field-of-view and zoom looks "neutral"
- */
-val CameraCharacteristics.neutralZoomPercent: Float
-  get() {
-    val zoomRange = if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.R)
-      this.get(CameraCharacteristics.CONTROL_ZOOM_RATIO_RANGE)
-    else null
-    return if (zoomRange != null)
-      ((1.0f - zoomRange.lower) / (zoomRange.upper - zoomRange.lower))
-    else
-      0.0f
-  }

example/src/CameraPage.tsx

@@ -95,18 +95,23 @@ export const CameraPage: NavigationFunctionComponent = ({ componentId }) => {
   }, [formats, fps, enableHdr]);
 
   //#region Animated Zoom
-  const formatMaxZoom = format?.maxZoom ?? 1;
-  const maxZoomFactor = Math.min(formatMaxZoom, MAX_ZOOM_FACTOR);
-  const neutralZoom = device?.neutralZoom ?? 0;
-  const neutralZoomScaled = (neutralZoom / maxZoomFactor) * formatMaxZoom;
-  const maxZoomScaled = (1 / formatMaxZoom) * maxZoomFactor;
+  // This just maps the zoom factor to a percentage value.
+  // so e.g. for [min, neutr., max] values [1, 2, 128] this would result in [0, 0.0081, 1]
+  const minZoomFactor = device?.minZoom ?? 1;
+  const neutralZoomFactor = device?.neutralZoom ?? 1;
+  const maxZoomFactor = device?.maxZoom ?? 1;
+  const maxZoomFactorClamped = Math.min(maxZoomFactor, MAX_ZOOM_FACTOR);
 
-  const cameraAnimatedProps = useAnimatedProps(
-    () => ({
-      zoom: interpolate(zoom.value, [0, neutralZoomScaled, 1], [0, neutralZoom, maxZoomScaled], Extrapolate.CLAMP),
-    }),
-    [maxZoomScaled, neutralZoom, neutralZoomScaled, zoom],
-  );
+  const neutralZoomOut = (neutralZoomFactor - minZoomFactor) / (maxZoomFactor - minZoomFactor);
+  const neutralZoomIn = (neutralZoomOut / maxZoomFactorClamped) * maxZoomFactor;
+  const maxZoomOut = maxZoomFactorClamped / maxZoomFactor;
+
+  const cameraAnimatedProps = useAnimatedProps(() => {
+    const z = interpolate(zoom.value, [0, neutralZoomIn, 1], [0, neutralZoomOut, maxZoomOut], Extrapolate.CLAMP);
+    return {
+      zoom: isNaN(z) ? 0 : z,
+    };
+  }, [maxZoomOut, neutralZoomOut, neutralZoomIn, zoom]);
   //#endregion
 
   //#region Callbacks
@@ -155,8 +160,8 @@ export const CameraPage: NavigationFunctionComponent = ({ componentId }) => {
   //#region Effects
   useEffect(() => {
     // Run everytime the neutralZoomScaled value changes. (reset zoom when device changes)
-    zoom.value = neutralZoomScaled;
-  }, [neutralZoomScaled, zoom]);
+    zoom.value = neutralZoomIn;
+  }, [neutralZoomIn, zoom]);
   //#endregion
 
   //#region Pinch to Zoom Gesture

ios/CameraView+AVCaptureSession.swift

@@ -68,7 +68,6 @@ extension CameraView {
       guard let videoDevice = AVCaptureDevice(uniqueID: cameraId) else {
         return invokeOnError(.device(.invalid))
       }
-      zoom = NSNumber(value: Double(videoDevice.neutralZoomPercent))
       videoDeviceInput = try AVCaptureDeviceInput(device: videoDevice)
       guard captureSession.canAddInput(videoDeviceInput!) else {
         return invokeOnError(.parameter(.unsupportedInput(inputDescriptor: "video-input")))

ios/CameraViewManager.swift

@@ -96,8 +96,8 @@ final class CameraViewManager: RCTViewManager {
           "hasFlash": $0.hasFlash,
           "hasTorch": $0.hasTorch,
           "minZoom": $0.minAvailableVideoZoomFactor,
+          "neutralZoom": $0.neutralZoomFactor,
           "maxZoom": $0.maxAvailableVideoZoomFactor,
-          "neutralZoom": $0.neutralZoomPercent,
           "isMultiCam": $0.isMultiCam,
           "supportsDepthCapture": false, // TODO: supportsDepthCapture
           "supportsRawCapture": false, // TODO: supportsRawCapture

ios/Extensions/AVCaptureDevice+neutralZoom.swift

@@ -9,6 +9,12 @@
 import AVFoundation
 
 extension AVCaptureDevice {
+  /**
+   Get the value at which the Zoom factor is neutral.
+
+   For normal wide-angle devices, this is always going to be 1.0, since this is the default scale.
+   For devices with an ultra-wide-angle camera, this value is going to be the value where the wide-angle device will switch over.
+   */
   var neutralZoomFactor: CGFloat {
     if #available(iOS 13.0, *) {
       if let indexOfWideAngle = self.constituentDevices.firstIndex(where: { $0.deviceType == .builtInWideAngleCamera }) {
@@ -19,14 +25,4 @@ extension AVCaptureDevice {
     }
     return 1.0
   }
-
-  /**
-   Get the value at which the Zoom value is neutral, in percent (0.0-1.0)
-
-   * On single-camera physical devices, this value will always be 0.0
-   * On devices with multiple cameras, e.g. triple-camera, this value will be a value between 0.0 and 1.0, where the field-of-view and zoom looks "neutral"
-   */
-  var neutralZoomPercent: CGFloat {
-    return (neutralZoomFactor - minAvailableVideoZoomFactor) / (maxAvailableVideoZoomFactor - minAvailableVideoZoomFactor)
-  }
 }

src/CameraDevice.ts

@@ -228,12 +228,20 @@ export interface CameraDevice {
    */
   maxZoom: number;
   /**
-   * The zoom percentage (`0.0`-`1.0`) where the camera is "neutral".
+   * The zoom factor where the camera is "neutral".
    *
-   * * For single-physical cameras this property is always `0.0`.
-   * * For multi cameras this property is a value between `0.0` and `1.0`, where the camera is in wide-angle mode and hasn't switched to the ultra-wide (`0.5`x zoom) or telephoto camera yet.
+   * * For single-physical cameras this property is always `1.0`.
+   * * For multi cameras this property is a value between `minZoom` and `maxZoom`, where the camera is in _wide-angle_ mode and hasn't switched to the _ultra-wide-angle_ (`0.5`x zoom) or telephoto camera yet.
    *
    * Use this value as an initial value for the zoom property if you implement custom zoom. (e.g. reanimated shared value should be initially set to this value)
+   * @example
+   * const device = ...
+   *
+   * const neutralZoomPercent = (device.neutralZoom - device.minZoom) / (device.maxZoom - device.minZoom)
+   * const zoomFactor = useSharedValue(neutralZoomPercent) // <-- initial value so it doesn't start at ultra-wide
+   * const cameraProps = useAnimatedProps(() => ({
+   *   zoom: zoomFactor.value
+   * }))
    */
   neutralZoom: number;
   /**