The Save method of the bitmap class has a parameter that lets you specify the file format, e.g.

generatedBmp.Save(fileName, ImageFormat.Jpeg)

This code should create a jpeg image:

[code]
private void Page_Load(object sender, System.EventArgs e)
{
  Response.ContentType = "image/jpeg";
  Response.Cache.SetCacheability(HttpCacheability.NoCache);

  // generate jpeg image ...
  FlowChart fc = (FlowChart)this.Session["fcx"];
  if (fc !=  null)
  {
  Bitmap bmp = fc.CreateBmpFromChart();

  // ... and send it to the browser
  EncoderParameters eps = new   EncoderParameters(1);
  eps.Param[0] = new EncoderParameter(   Encoder.Quality, (long)98 );
  ImageCodecInfo codec = GetEncoderInfo(Response.ContentType);
  bmp.Save(Response.OutputStream, codec, eps);
  bmp.Dispose();
}

  Response.OutputStream.Close();
}
[/code]

It sets the http response type to "image/jpeg" and uses an encoder for the "image/jpeg" MIME type to create the image data. Now that might be a problem in the browser if it determines the image type by the linked image file name extension and not by the MIME type.

Hi,

It will throw an exception if try to save as PNG format. The following is my code snipet:

private void Page_Load(object sender, System.EventArgs e)
{
  Response.ContentType = "image/png";
  Response.Cache.SetCacheability(HttpCacheability.NoCache);

  // generate jpeg image ...
  FlowChart fc = (FlowChart)this.Session["fcx"];
  if (fc !=  null)
  {
    Bitmap bmp = fc.CreateBmpFromChart();
    bmp.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Png);
    bmp.Dispose();
  }
  Response.OutputStream.Close();
}

I think the exception type is "System.Runtime.InteropServices.ExternalException". The StackTrace is shown below:
    at System.Drawing.Image.Save(Stream stream, ImageCodecInfo encoder, EncoderParameters encoderParams)
    at System.Drawing.Image.Save(Stream stream, ImageFormat format)
    at WebApp.ImageGen.Page_Load(Object sender, EventArgs e)

It works now. Thanks to you.

- Erison

Daniel,

FireFox saves the generated image as a jpeg, and both IE6 and IE7 save it as bmp. So it seems that's an IE problem. You might try mapping an http://.../diag.jpg URL to the ASP page that generates the image. Probably that will be a better clue to IE that the image is a jpeg than the mime type. Or just create temporary images in a server folder and make the IMG tags link to these images.

Stoyan