Converting a PNG returned from an API to a JPG, then to a Base64 encoded string in an Azure function

Question

I'm currently writing a function that, when executed, calls an API which returns a PNG image. I want to then take that image. Convert it to a JPEG and URL encode it before returning it as a response from the function.

I'm relatively new when working with Azure function, so directions for good pieces of documentation would be greatly appreciated.

 private static string _websiteurl = "https://studentSystem/";

        [FunctionName("Function1")]
        public static async Task<IActionResult> Run([HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = null)] HttpRequest req, ILogger log)
        {


            var endPointString = "/v1/students/12162333/id-card-photos";

            using var client = new HttpClient();
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("image/png"));
            var url = new Uri(_websiteurl + endPointString);

            var response = await client.GetAsync(url);
            response.EnsureSuccessStatusCode();


            return null //Jpeg as URL encoded
        }

Does anyone know of a good way to directly do this just in memory? I can think of a way that involves saving the file and then reading it again but that doesn't seem to be very efficient and I would like to avoid it if possible. Is converting it to jpeg then URL encoding better then the other way round?

Regards.

Answer 1

I Solved it using System.Drawing.Image and the memoryStream class.

            using var client = new HttpClient();

            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("image/png"));

            // replace Url with your URL
            var response = await client.GetAsync(WebsiteUrl);
            response.EnsureSuccessStatusCode();

            string base64String = null;

            await using (var stream = new MemoryStream())
            {
                var image = Image.FromStream(await response.Content.ReadAsStreamAsync());
                image.Save(stream, ImageFormat.Jpeg);
                stream.Position = 0;
                base64 = Convert.ToBase64String(stream.ToArray());

            }

            //
             return new OkObjectResult(base64);