Load images seamlessly from internal storage in unity android?

bhavin2707

I have been working on a puzzle game for the android device using Unity Game Engine, and I have been facing issues with loading the images from internal storage. The game has like 400-500 levels. Which are downloaded at runtime as per demand, and stored in the internal storage. The problem occurs in loading these images. Loading images from internal storage is very expensive. The function that is responsible for downloading or loading images is below,

public IEnumerator DownloadOrLoadImage(string link, string dirName, int index = -1)
{
    if (!loadFromResources)
    {
        int startPos = link.LastIndexOf("https://drive.google.com/file/d/") + "https://drive.google.com/file/d/".Length;
        int length = link.IndexOf("/view?usp=sharing") - startPos;
        if (length >= 1)
        {
            string ID = link.Substring(startPos, length);

            link = "https://drive.google.com/uc?export=download&id=" + ID;

            if (File.Exists(Application.persistentDataPath + "/.cache/" + ID))
            {
                if (index != -1 && index == LevelMenuLoader.instance.totalJsonCount)
                {
                    LevelMenuLoader.instance.AfterMenuDownloadSequence();
                }
                print("Loading from the device");

                UnityWebRequest request = UnityWebRequestTexture.GetTexture("file://" + Application.persistentDataPath + "/.cache/" + ID);
                yield return request.SendWebRequest();

                if (request.result != UnityWebRequest.Result.Success)
                {
                    Debug.Log(request.error);
                }
                else
                {
                    byte[] bytes = ((DownloadHandlerTexture)request.downloadHandler).data;

                    if (bytes.Length > 1)
                        this.GetComponent<RawImage>().texture = ((DownloadHandlerTexture)request.downloadHandler).texture;
                }

                request.downloadHandler.Dispose();
                request.Dispose();
                isImageDownloaded = true;
            }
            else
            {
                LevelMenuLoader.instance.AfterMenuDownloadSequence();

                using (UnityWebRequest request = UnityWebRequestTexture.GetTexture(link))
                {
                    yield return request.SendWebRequest();

                    if (request.isNetworkError || request.isHttpError)
                        Debug.Log(request.error);
                    else
                    {
                        this.GetComponent<RawImage>().texture = ((DownloadHandlerTexture)request.downloadHandler).texture;

                        byte[] bytes = ((DownloadHandlerTexture)request.downloadHandler).data;
                        if (bytes.Length > 1)
                        {
                            File.WriteAllBytes(Application.persistentDataPath + "/.cache/" + ID, bytes);
                            isImageDownloaded = true;
                        }

                        request.downloadHandler.Dispose();
                        request.Dispose();
                    }
                }
            }
        }
    }
    else
    {
        this.GetComponent<RawImage>().texture = Resources.Load<Texture>("Levels/" + dirName + "/" + this.GetComponent<LevelInformation>().m_LevelID);
    }

When it comes to loading 300+ images, it's seriously a headache and it takes up to 3-4 seconds to load the images, and in some devices, it won't load at all because of some memory usage limitations in some devices. It will really help if someone can help or guide me to optimize the code in a way that is very seamless and faster to load images.

PS: I have tried object pooling for scroll view, so I only load the images that are needed and dispose of them when they are not visible on the screen. But it's impractical as loading the image creates a bit of lag and it's not as fast as needed. Any suggestion will be great.

Thank you.