[Unity] Save RenderTexture to image file

ConvertTextureToPng.cs

using UnityEngine;
using UnityEditor;

public class ConvertTextureToPng
{
    const string MenuName = "Assets/Save Texture to png";

    [MenuItem(MenuName)]
    public static void SaveRTToFile()
    {
        var selected = Selection.activeObject;
        if(!(selected is Texture2D tex))
        {
            if(selected is RenderTexture rt)
            {
                RenderTexture.active = rt;
                tex = new Texture2D(rt.width, rt.height, TextureFormat.RGB24, false);
                tex.ReadPixels(new Rect(0, 0, rt.width, rt.height), 0, 0);
                RenderTexture.active = null;
            }
            else throw new System.NotImplementedException("object type : " + Selection.activeObject);
        }

        var sourcePath = AssetDatabase.GetAssetPath(selected);
        if(!tex.isReadable)
        {
            var source = tex;
            tex = new Texture2D(source.width,source.height,source.format,true);
            Graphics.CopyTexture(source,tex);
        }
        
        var bytes = tex.EncodeToPNG();

        string path = AssetDatabase.IsMainAsset(selected) ? (sourcePath + ".png") : (sourcePath + "." + selected.name + ".png");
        System.IO.File.WriteAllBytes(path, bytes);
        AssetDatabase.ImportAsset(path);
        Debug.Log("Saved to " + path);
    }

    [MenuItem(MenuName, true)]
    public static bool SaveRTToFileValidation()
    {
        return Selection.activeObject is Texture2D or RenderTexture;
    }
}

SaveScreenshotToFile.cs

using UnityEngine;
using UnityEditor;

public class SaveScreenshotToFile {
    [MenuItem("Custom/Render Camera to file")]
    public static void RenderCameraToFile()
    {
        Camera camera = Selection.activeGameObject.GetComponent<Camera>();
        
        RenderTexture rt = new RenderTexture(2560, 1440, 24, RenderTextureFormat.ARGB32, RenderTextureReadWrite.sRGB);
        RenderTexture oldRT = camera.targetTexture;
        camera.targetTexture = rt;
        camera.Render();
        camera.targetTexture = oldRT;
        
        RenderTexture.active = rt;
        Texture2D tex = new Texture2D(rt.width, rt.height, TextureFormat.RGB24, false);
        tex.ReadPixels(new Rect(0, 0, rt.width, rt.height), 0, 0);
        RenderTexture.active = null;
        
        byte[] bytes = tex.EncodeToPNG();
        string path = "Assets/screenshot.png";
        System.IO.File.WriteAllBytes(path, bytes);
        AssetDatabase.ImportAsset(path);
        Debug.Log("Saved to " + path);
    }
    
    [MenuItem("Custom/Render Camera to file", true)]
    public static bool RenderCameraToFileValidation()
    {
        return Selection.activeGameObject != null && Selection.activeGameObject.GetComponent<Camera>() != null;
    }
}