LUT default image generator on Unity editor.

LookupTextureGenerator.cs

// https://gist.github.com/WonkyKIM/58c75a3226e1e84e8b1af2167accfe1f

#if UNITY_EDITOR

using System.IO;
using UnityEditor;
using UnityEngine;

public class LookupTextureGenerator : MonoBehaviour {
    
    private enum LUTSizeList {
        LDR16,
        LDR32
    }

    [SerializeField] private static string path = "Textures";
    [SerializeField] private static string filename = "LUT_default";


    [MenuItem("Tools/Generate LUT/LDR16")]
    public static void Create16() {
        CreateLookUpTexture(LUTSizeList.LDR16);
    }

    [MenuItem("Tools/Generate LUT/LDR32")]
    public static void Create32() {
        CreateLookUpTexture(LUTSizeList.LDR32);
    }


    private static void CreateLookUpTexture(LUTSizeList _size) {
        int resolution = GetResolutionFromList(_size);
        Texture2D texture = new Texture2D(resolution * resolution, resolution, TextureFormat.RGB24, false);

        // Set pixel values
        float step = 1.0f / (resolution - 1);
        for(int z = 0; z<resolution; z++) {
            for(int y = 0; y < resolution; y++) {
                for(int x = 0; x < resolution; x++) {
                    int ix = x + z*resolution;
                    int iy = y;
                    Color color = new Color(x * step, y * step, z * step);
                    texture.SetPixel(ix, iy, color);
                }
            }
        }

        texture.Apply();

        // Encode texture into PNG
        // https://docs.unity3d.com/ScriptReference/ImageConversion.EncodeToPNG.html
        byte[] bytes = texture.EncodeToPNG();
        //Object.Destroy(texture);

        string filePath = $"{Application.dataPath }/{path}";
        if(!Directory.Exists(filePath)) {
            Directory.CreateDirectory(filePath);
        }

        string file = $"{filePath}/{filename}_{_size.ToString()}.png";
        File.WriteAllBytes(file, bytes);

        Debug.Log($"LUT File has been generated into <color=green>'{file}'.</color>");
    }


    private static int GetResolutionFromList(LUTSizeList _size) {
        switch(_size) {
            case LUTSizeList.LDR16:
                return 16;
            case LUTSizeList.LDR32:
                return 32;
            default:
                return 16;
        }
    }

}

#endif