Cannot render image to HttpContext.Response.OutputStream

Question

Basically I am trying to render a simple image in an ASP.NET handler:

public void ProcessRequest (HttpContext context)
{
    Bitmap image = new Bitmap(16, 16         


        

Answer 1

Image.Save(MemoryStream stream) does require a MemoryStream object that can be seeked upon. The context.Response.OutputStream is forward-only and doesn't support seeking, so you need an intermediate stream. However, you don't need the byte array buffer. You can write directly from the temporary memory stream into the context.Response.OutputStream:

/// 

/// Sends a given image to the client browser as a PNG encoded image.
/// 
/// The image object to send.
private void SendImage(Image image)
{
    // Get the PNG image codec
    ImageCodecInfo codec = GetCodec("image/png");

    // Configure to encode at high quality
    using (EncoderParameters ep = new EncoderParameters())
    {
        ep.Param[0] = new EncoderParameter(Encoder.Quality, 100L);

        // Encode the image
        using (MemoryStream ms = new MemoryStream())
        {
            image.Save(ms, codec, ep);

            // Send the encoded image to the browser
            HttpContext.Current.Response.Clear();
            HttpContext.Current.Response.ContentType = "image/png";
            ms.WriteTo(HttpContext.Current.Response.OutputStream);
        }
    }
}

A fully functional code sample is available here:

Auto-Generate Anti-Aliased Text Images with ASP.NET