If you want to dynamically generate an image and display the image in a Web Page, then you actually need to create two ASP.NET pages. You create one page that generates the byte data for the actual image.
This page is then displayed in a second page, the display page, with an HTML <img> tag.
This example creates a pair of pages that displays a red circle. We'll generate a GIF image for the circle in an ASP.NET page named Circle.aspx.
<%@ Page ContentType="image/gif" %>
<%@ Import namespace="System.Drawing" %>
<%@ Import namespace="System.Drawing.Imaging" %>
The purpose of the ContentType directive that appears at the very top of the page is to actually pretend that ASP .NET page to be a GIF image. When the page is requested, the ContentType directive tells the Web browser that it should expect a GIF image instead of a normal HTML page.
Normally you will need to open the page in a second page to use it effectively in a web page.
The second page contains an HTML <img> tag that loads the above page. This page contains normal HTML content that appears around the image.
<h1>Here is an image:</h1>
<h1>The image appears above!<h1>
The Web browser treats the Circle.aspx page as a normal GIF image. It has no idea that the image was dynamically generated in an ASP.NET page.