Wednesday, August 17, 2016

How to read images from a URL in asp.net core

Hi,

I was building an asp.net core web api that suppose to read images from an external url. Even though i have done this dozens of time. I got stuck for a bit trying to have the same code that reads an image from a url into my asp.net core project using Visual Studio 2015.

After little bit of searching, i found out that before trying to read a static file such as an image from your controller. you need to enable first Directory browsing and configure routing path so you are able to view this image in a browser by hitting the url of the image.


So, follow these below steps to be able to read images from a url (in my case these images were part of project):

1) Move images folder (or any static files folder) under wwwroot folder.
2) Open startup.cs file and enable directory browsing.


C# code to enable directory browsing and serving static files:

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
        {
            loggerFactory.AddConsole(Configuration.GetSection("Logging"));
            loggerFactory.AddDebug();
            app.UseApplicationInsightsRequestTelemetry();
            app.UseApplicationInsightsExceptionTelemetry();

            // Enable directory browsing
            app.UseStaticFiles();
            app.UseStaticFiles(new StaticFileOptions()
            {
                FileProvider = new PhysicalFileProvider(
           Path.Combine(Directory.GetCurrentDirectory(), @"wwwroot\images")),
                RequestPath = new PathString("/images")
            });
         
            app.UseDirectoryBrowser(new DirectoryBrowserOptions()
            {
                FileProvider = new PhysicalFileProvider(
            Path.Combine(Directory.GetCurrentDirectory(), @"wwwroot\images")),
                RequestPath = new PathString("/images")
            });

            app.UseMvc();
        }

3) Run your app and try to load an image from the browser, for example:
http://localhost:12354/images/test1.jpg

4) You will be able to view the image in the browser. now, let's read image in C# from a url.

 // read from remote image drive
                    using (HttpClient c = new HttpClient())
                    {
                        using (Stream s = await c.GetStreamAsync(imgUrl))
                        {
                             // do any logic with the image stream, save it, store it...etc.
                        }
                    }

If you haven't done step #3 (This is were i got stuck!), the GetStreamAsync method will throw an exception (404 not found) error because we haven't configured the app to deliver static files.

Hope this helps!

References:
1) Working with static files in asp.net core:
https://docs.asp.net/en/latest/fundamentals/static-files.html#enabling-directory-browsing

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