c# - 如何在 Web API 中通过外部源获取图像并以 base64 返回？

Question

我需要调用外部 API 并检索 png 图像，然后以 base64 字符串形式返回该图像。如何读取响应消息作为图像并将其转换为 base64？

这是我目前所拥有的:

[HttpGet()]
[Route("test")]
public async Task<string> GetValidationImage()
{
   using (var client = new HttpClient())
   {
    //grab image from external API as png
    client.BaseAddress = new Uri(TestBaseAddress);
    client.DefaultRequestHeaders.Accept.Clear();
    client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("image/png"));

    return response = await client.GetAsync(TestString);
   }
}

Answer 1

弄清楚了，必须将其流式传输到图像对象。

[HttpGet()]
[Route("test")]
public async Task<string> GetValidationImage()
{
   string base64String;
   client.BaseAddress = new Uri(TestBaseAddress);
   client.DefaultRequestHeaders.Accept.Clear();
   client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("image/png"));

   var response = await client.GetAsync(TestString);

   using (var ms = new MemoryStream())
   {
      var image = System.Drawing.Image.FromStream(await response.Content.ReadAsStreamAsync());
      image.Save(ms, ImageFormat.Png);
      var imageBytes = ms.ToArray();
      base64String = Convert.ToBase64String(imageBytes);
   }

   return base64String;
}