A custom HTTP handler to produce Pix-It images.

PixItHandler.cs

public class PixItHandler : IHttpHandler
{

  public bool IsReusable
  {
    get { return true; }
  }

  public void ProcessRequest(HttpContext context)
  {
    string json = ReadJson(context.Request.InputStream);
    var data = ToPixItData(json);
    WriteResponse(context.Response, ToBuffer(CreateImage(data)));
  }

  private static PixItData ToPixItData(string json)
  {
    JObject o = JObject.Parse(json);
    int size = o.SelectToken("pixelSize").Value<int>();
    int wide = o.SelectToken("pixelsWide").Value<int>();
    int high = o.SelectToken("pixelsHigh").Value<int>();
    JToken bg = o.SelectToken("background");
    Color? bgColor = null;
    if (bg != null)
    {
      string bgStr = bg.Value<string>();
      bgColor = ColorTranslator.FromHtml(bgStr);
    }
    JToken payload = o.SelectToken("payload");
    var dict = new Dictionary<Color, IEnumerable<Pixel>>();
    foreach (var token in payload)
    {
      var list = new List<Pixel>();
      foreach (var xyArray in token.SelectToken("pixels"))
      {
        int x = xyArray[0].Value<int>();
        int y = xyArray[1].Value<int>();
        list.Add(new Pixel(x, y));
      }
      string cs = token.SelectToken("color").Value<string>();
      Color clr = ColorTranslator.FromHtml(cs);
      dict[clr] = list;
    }
    return new PixItData(wide, high, size, dict);
  }

  private static Image CreateImage(PixItData data)
  {
    int width = data.PixelSize * data.PixelsWide;
    int height = data.PixelSize * data.PixelsHigh;
    var image = new Bitmap(width, height);
    using (Graphics g = Graphics.FromImage(image))
    {
      if (data.Background.HasValue)
      {
        Color bgColor = data.Background.Value;
        using (var brush = new SolidBrush(bgColor))
        {
          g.FillRectangle(brush, 0, 0, 
            data.PixelSize * data.PixelsWide, 
            data.PixelSize * data.PixelsHigh);
        }
      }
      foreach (Color color in data.Data.Keys)
      {
        using (var brush = new SolidBrush(color))
        {
          foreach (Pixel p in data.Data[color])
          {
            g.FillRectangle(brush,
              p.X*data.PixelSize,
              p.Y*data.PixelSize,
              data.PixelSize,
              data.PixelSize);
          }
        }
      }
    }
    return image;
  }

  private static string ReadJson(Stream s)
  {
    s.Position = 0;
    using (var inputStream = new StreamReader(s))
    {
      return inputStream.ReadToEnd();
    }
  }

  private static byte[] ToBuffer(Image image)
  {
    using (var ms = new MemoryStream())
    {
      image.Save(ms, ImageFormat.Png);
      return ms.ToArray();
    }
  }

  private static void WriteResponse(HttpResponse response, 
    byte[] buffer)
  {
    response.ContentType = "image/png";
    response.BinaryWrite(buffer);
    response.Flush();
  }

}