[2005] Custom Webcontrol

I'm wondering if there is a way that I would be able to create a graphic image during the rendering of the webcontrol? For example in the render method I render a image, but for the source I would like to basically perform a binary write much like that when you would pull an image blob from a database. is there some way of doing this? There reason I'm asking it I would like to create a control that would draw string that the user would have to enter when submitting information, much like that of what you see on site's now when you are required to enter the security code for submitting.