How to cache images to disk that were retrieved via a custom image provider

[tekguy]

Hello,

I've setup a custom ImageProvider and ImageResolver, right now this works as expected. Whenever I hit the endpoint /custom/blah/github.jpg, I create an HttpClient request to download the image.

But when the same image is requested again, I would like for it to use the version on the disk (for 30 seconds), I was told by @JimBobSquarePants to use this forum instead of Glitter chat. Any help would be greatly appreciated.

public class MyCustomImageProvider : IImageProvider
{
    private readonly IFileProvider fileProvider;

    private readonly FormatUtilities formatUtilities;

public MyCustomImageProvider(
        IWebHostEnvironment environment,
        FormatUtilities formatUtilities)
    {
        this.formatUtilities = formatUtilities;
    }
    
    public Func<HttpContext, bool> Match { get; set; } = x => x.Request.Path.Value.Contains("custom/");

    public bool IsValidRequest(HttpContext context) => this.formatUtilities.GetExtensionFromUri(context.Request.GetDisplayUrl()) != null;

    public async Task<IImageResolver> GetAsync(HttpContext context)
    {
        // Path has already been correctly parsed before here.
        var filePath = context.Request.Path.Value;
        var filePathArray = filePath.Split('/');

        if (filePathArray[2].Equals("blah", StringComparison.OrdinalIgnoreCase) && !string.IsNullOrEmpty(filePathArray[3]))
        {
            var downloadUrl = $"https://MYPRIVATESITE/{filePathArray[3]}";
            var client = new HttpClient();
            var data = await client.GetStreamAsync(downloadUrl);

            var metadata = new ImageMetadata(DateTime.Now.AddSeconds(30));
            return new MyCustomImageResolver(data, metadata);
        }

        return null;

        //// Check to see if the file exists.
        //if (!fileInfo.Exists)
        //{
        //    return Task.FromResult<IImageResolver>(null);
        //}

    }

    public ProcessingBehavior ProcessingBehavior { get; } = ProcessingBehavior.All;
}

Here is the image resolver:

public class MyCustomImageResolver : IImageResolver
{
    private readonly Stream stream;
    private readonly ImageMetadata metadata;

    public MyCustomImageResolver(Stream stream, in ImageMetadata metadata)
    {
        this.stream = stream;
        this.metadata = metadata;
    }
    public Task<ImageMetadata> GetMetaDataAsync()
    {
        //Response<BlobProperties> properties = await this.stream.;
        //return new ImageMetadata(properties?.Value.LastModified.DateTime ?? DateTime.UtcNow);
        return Task.FromResult(metadata);
    }

    public Task<Stream> OpenReadAsync() => Task.FromResult(this.stream);
}

And finally my ConfigureServices:

public void ConfigureServices(IServiceCollection services)
{
    services.AddImageSharpCore(options => {
        options.MaxBrowserCacheDays = 1;
    })
        .SetRequestParser<QueryCollectionRequestParser>()
        .Configure<PhysicalFileSystemCacheOptions>(options =>
        {
            options.CacheFolder = "is-cache";
        })
        .SetCache(provider =>
        {
            return new PhysicalFileSystemCache(
                provider.GetRequiredService<IOptions<PhysicalFileSystemCacheOptions>>(),
                provider.GetRequiredService<IWebHostEnvironment>(),
                provider.GetRequiredService<IOptions<ImageSharpMiddlewareOptions>>(),
                provider.GetRequiredService<FormatUtilities>());
        })
        .SetCacheHash<CacheHash>()
        .AddProvider<MyCustomImageProvider>()
        .AddProcessor<ResizeWebProcessor>()
        .AddProcessor<FormatWebProcessor>()
        .AddProcessor<BackgroundColorWebProcessor>();
}

[JimBobSquarePants]

Hi @tekguy

You need to implement your own cache. The PhysicalFileSystemCache cache stores images for days not seconds.

On a side note you should be using UTC date for your metadata.

[JimBobSquarePants]

Actually.... That won't help. Let me have a think, it might be simple to add minutes and seconds values to the middleware options.

[JimBobSquarePants]

Hi @tekguy

I've refactored the cache to use two new properties BrowserMaxAge and CacheMaxAge. You'll be able to set either to use any supported TimeSpan configuration.

[tekguy]

@JimBobSquarePants thank you I will take a look at it

[JimBobSquarePants]

https://www.myget.org/feed/sixlabors/package/nuget/SixLabors.ImageSharp.Web/1.0.0-rc.3.8