hk3.cs

public class ImageController : ApiController
{
    [HttpGet]
    public HttpResponseMessage getImg() {
        string ImgPath = @"D:\CSharp\MyWebAPI\MyWebAPI\App_Data\123.jpg";
        var resp = new HttpResponseMessage();
        resp.Content = new StreamContent(File.OpenRead(ImgPath));
        resp.Content.Headers.ContentType = new MediaTypeHeaderValue("image/jpg");
        return resp;
    }
}