C# .jpg help pls

Can i get some help?
I am making a program in c# that hides strings into images by changing each pixel color to be odd or even so i can store binary data in the pixels without changing the over all look of the image. Its just something i am making for fun but it only seems to work with .bmp's. I want to get it working with .jpg but i dont know how to do this. Right now i am just using System.Drawing.Bitmap to modify the images. Is their any other way that i can do this so it will be compatible with .jpg?

http://news.yahoo.com/s/livescience/20100630/sc_livescience/russianspieshidsecretcodesinonlinephotos

Although the exact details of what the supposed Russian agents embedded in the pictures, and how they did it, remains classified, the basic technique involves changing the numeric code that computers assign to colors, explained Tal Malkin, an assistant professor in Columbia University's cryptography laboratory.

To generate the picture on a computer screen, the computer assigns every pixel three numeric values that correspond to the amount of red, green or blue in the color the pixel displays. By changing those values ever so slightly, the spies could hide the 1's and 0's of computer language in the picture's pixel numbers, but without altering the picture's appearance to the human eye, Bellovin said.

back to /russia/, please