react-native-vision-camera/src/RotationHelper.ts

A powerful, high-performance React Native Camera library.

import type { Orientation } from './types/Orientation'

function orientationToDegrees(orientation: Orientation): number {
  switch (orientation) {
    case 'portrait':
      return 0
    case 'landscape-right':
      return 90
    case 'portrait-upside-down':
      return 180
    case 'landscape-left':
      return 270
  }
}

export class RotationHelper {
  /**
   * Gets or sets the current preview orientation.
   */
  previewOrientation: Orientation = 'portrait'
  /**
   * Gets or sets the current output orientation.
   */
  outputOrientation: Orientation = 'portrait'

  /**
   * Gets the current target rotation (in degrees) that needs to be applied
   * to all UI elements so they appear up-right.
   */
  get uiRotation(): number {
    const previewDegrees = orientationToDegrees(this.previewOrientation)
    const outputDegrees = orientationToDegrees(this.outputOrientation)
    const diffDegrees = (outputDegrees - previewDegrees) % 360

    if (diffDegrees < -180) {
      // Changes e.g. -270 to +90, so it is a shorter rotation on UI
      return diffDegrees + 360
    } else if (diffDegrees > 180) {
      // Changes e.g. +270 to -90, so it is a shorter rotation on UI
      return diffDegrees - 360
    } else {
      // It is a short rotation already, return it
      return diffDegrees
    }
  }
}