CameraAspectRatioMinMax.cs

using System;
using System.Collections;
using System.Collections.Generic;
using Sirenix.OdinInspector;
using UnityEngine;

public class CameraAspectRatioMinMax : MonoBehaviour
{
    [BoxGroup("Render Camera")]
    [Required] [SerializeField] private Camera cam;
   
    [BoxGroup("Border colour")]
    [Required] [SerializeField] private Camera dummyCamera;
    [SerializeField] private Color barColor = Color.black;
    
    [BoxGroup("Ratio Limits")]
    [SerializeField, MinValue(0.5f), MaxValue(5f)] private float minRatio = 1.5f;
    [SerializeField, MinValue("minRatio"), MaxValue(5f)] private float maxRatio = 2.4f;
    
    [BoxGroup("Repeat Timer")]
    [SerializeField] private bool repeatAutomatically = false;
    [SuffixLabel("seconds")][SerializeField] private float repeatTimer = 0.5f;
    [ReadOnly][SerializeField] private bool isRunning = true; 

    [BoxGroup("Current Sizes")]
    [ReadOnly][SerializeField] private Vector2Int viewportSize;
    [ReadOnly][SerializeField] private float viewportAspectRatio = 1.777f;
    [ReadOnly][SerializeField] private Rect cameraRect;
    
    private void Update()
    {
        if (isRunning) return;
        if (!repeatAutomatically) return;
        StopAllCoroutines();
        StartCoroutine(RepeatTimer());
    }


    [Button]
    void SetupDummyCamera()
    {
        if (dummyCamera == null)
        {
            GameObject aspectBarColor = new GameObject("Aspect Bar Color");
            dummyCamera = aspectBarColor.AddComponent<Camera>();
            aspectBarColor.transform.parent = transform;
        }
        dummyCamera.clearFlags = CameraClearFlags.SolidColor;
        dummyCamera.backgroundColor = barColor;
        dummyCamera.cullingMask = (LayerMask)0;
        dummyCamera.depth = -99; 
    }
    
    
    [Button]
    void UpdateCameraViewport()
    {
        cam.rect = new Rect(0, 0, 1, 1);
        var size = Screen.currentResolution;
        viewportSize = new Vector2Int(cam.pixelWidth, cam.pixelHeight);
        viewportAspectRatio = GetAspect(viewportSize.x, viewportSize.y);
        
        // resolution has changed
        RefreshAspectRatio();
    }
    
    public bool CheckHasChanged()
    {
        return (viewportSize.y != cam.pixelHeight || viewportSize.x != cam.pixelWidth);
    }
    
    [Button]
    void ResetCamera()
    {
        cam.rect = new Rect(0, 0, 1, 1);
    }
    

    public void RefreshAspectRatio()
    {
        // aspect ratio is within limits 
        if (viewportAspectRatio < maxRatio && viewportAspectRatio > minRatio) 
            return;

        // letterbox (horizontal bars)
        if (viewportAspectRatio < minRatio)
        {
            CameraSetWidthHeight(1f, viewportAspectRatio / minRatio);
            return;
        }

        // pillarbox (side bars)
        CameraSetWidthHeight(maxRatio / viewportAspectRatio, 1f);
    }

    void CameraSetWidthHeight(float width, float height)
    {
        cameraRect.Set((1f - width) * 0.5f, (1f - height) * 0.5f, width, height);
        cam.rect = cameraRect;
    }

    float GetAspect(float width, float height)
    {
        return width / height;
    }

    IEnumerator RepeatTimer()
    {
        isRunning = true;
        while (repeatAutomatically)
        {
            if (CheckHasChanged()) UpdateCameraViewport();
            yield return new WaitForSeconds(repeatTimer);
        }

        isRunning = false;
    }
    
}