yichael_smartbow/Assets/JC/Untiy/UI/BackgroundAdapter.cs

using UnityEngine;
using UnityEngine.UI;

namespace JC.Unity.UI {
    public class AdapterUtils
    {
        public static void MakeRectTransformFullScreen(MonoBehaviour mono) {
            RectTransform rtf = mono.GetComponent<RectTransform>();
            rtf.anchorMin = Vector2.zero;
            rtf.anchorMax = new Vector2(1, 1);
            rtf.offsetMin = Vector2.zero;
            rtf.offsetMax = Vector2.zero;
        }
    }
    public class RectTransformUtils
    {   
        public static Vector3 CanvasV3ToScreenV3(Vector3 vector3, RectTransform rectTransform) {
            Vector2 canvasSize = rectTransform.GetComponentInParent<CanvasScaler>().GetComponent<RectTransform>().sizeDelta;
            vector3.y *= Screen.height / canvasSize.y;
            vector3.x *= Screen.width / canvasSize.x;
            return vector3;
        }
        public static Vector3 ScreenV3ToCanvasV3(Vector3 vector3, RectTransform rectTransform) {
            Vector2 canvasSize = rectTransform.GetComponentInParent<CanvasScaler>().GetComponent<RectTransform>().sizeDelta;
            vector3.y *= canvasSize.y / Screen.height;
            vector3.x *= canvasSize.x / Screen.width;
            return vector3;
        }
        public static Vector3 GetPositionByPivot(RectTransform rectTransform, Vector2 pivot) {
            Vector2 sizeInScreen = CanvasV3ToScreenV3(rectTransform.rect.size, rectTransform);
            Vector2 deltaPivot = pivot - rectTransform.pivot;
            Vector3 deltaPos = sizeInScreen * deltaPivot;
            return rectTransform.position + deltaPos;
        }
    }   
    [ExecuteAlways]
    public class BackgroundAdapter : MonoBehaviour
    {
        private CanvasScaler _scaler;

        void Start()
        {
            UpdateScale();
        }

        #if UNITY_EDITOR
        void Update()
        {
            UpdateScale();
        }
        #endif

        void UpdateScale()
        {
            if (_scaler == null) _scaler = GetComponentInParent<CanvasScaler>();
            if (_scaler == null) return;
            var resolution = _scaler.referenceResolution;
            var rt = _scaler.transform as RectTransform;
            if (rt == null) return;
            var screenSize = rt.sizeDelta;
            var factor = Mathf.Max(screenSize.x / resolution.x, screenSize.y / resolution.y);
            var scale = Vector3.one * factor;
            transform.localScale = scale;
        }
    }
}