In .net the Bitmap class covers more general concept: (theoretically) all raster images. As you can see here:
http://msdn.microsoft.com/en-us/library/at62haz6.aspx[
^], .net
bitmap object[
^] supports by default several raster image formats, including jpeg. When you try to read pixel data, you will get the proper value (depending on pixel format too), indifferent of the file format your loaded image had.