DevILWrapperClient.cs

using System.Runtime.InteropServices;
using System;
using UnityEngine;
using System.Drawing;


public class TextureSlicer : MonoBehaviour
{
    [DllImport("DevILWrapper.dll", CallingConvention = CallingConvention.Cdecl)]
    public static extern IntPtr getImagedata(string filePath, out int width, out int height);

    void Start()
    {
        int width, height;
        IntPtr imageData = getImagedata("C:\\Users\\chakm\\OneDrive\\Desktop\\testb.png", out width, out height);

        int arraySize = (width * height * 3) + 6;

        byte[] managedArray = new byte[arraySize];
        Marshal.Copy(imageData, managedArray, 0, arraySize);

        for (int i = 0; i < arraySize; i++)
        {
            Debug.Log(managedArray[i]);
        }
    }

    void Update()
    {

    }
}