Dynamically Generate Images in Web Pages

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.



<html>

      <head><title>DisplayCircle.aspx</title></head>


      <body>


            <h1>Here is an image:</h1>


            <img src="Circle.aspx">


            <h1>The image appears above!<h1>


      </body>


</html>



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.



 









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