Question

I have an ASP.NET web form. This web form has an event handler that generates some HTML. This HTML is based on the time-of-day, that is why it is created in the event handler. Based on the time of day, an image is created programmatically via the following method:

private Bitmap GetImageForTime(DateTime time)
{
  Bitmap bitmap = new Bitmap();

  // Dynamically build the bitmap...

  return bitmap;
}

I want to call this method when the HTML is being generated. However, I do NOT want to write the image on the server. Instead, I would like to figure out a way to write it out along with the HTML. In a sense, I’m trying to accomplish the following:

protected void myLiteral_Load(object sender, EventArgs e)
{
  string html = "<table><tr><td>";
  html += GetImageForTime(DateTime.Now);  // This is the problem because it's binary.
  html += "</td><td>";
  html += GetWeatherHtmlText();
  html += "</td></tr></table>";
  myLiteral.Text = html;
}

Is this possible? If so, how?

Answer 1

Create another aspx page called TimeImage.aspx then in the Page_Load of the code-behind for the page put this code:

void Page_Load(object sender, EventArgs args) {
    string mime = "image/jpeg";
    Response.ContentType = mime;

    Bitmap b = GetImageForTime(DateTime.Now);

    var codec = ImageCodecInfo.GetImageEncoders().Where(i => i.MimeType == mime).SingleOrDefault();

    if(codec != null)
        b.Save(Response.OutputStream, codec, null);
}

Then make your html generation look like this:

protected void myLiteral_Load(object sender, EventArgs e)
{
  string html = "<table><tr><td>";
  html += "<img src='TimeImage.aspx'>"
  html += "</td><td>";
  html += GetWeatherHtmlText();
  html += "</td></tr></table>";
  myLiteral.Text = html;
}

This will create an img tag that calls the TimeImage.aspx page, that page changes the response mime-type to image/jpeg, converts your bitmap to a JPG, and then saves it to the response output stream so that the image tag can display it as a JPG.

If you prefer a different format just change the mime type at the top (e.g. “image/gif” for GIF, or “image/png” for PNG).