http://iysm.net/?p=7

here is a good tutorial for using jpeglib to do decode and encode. It states the usage of some common parameter of decode and encode.

http://blog.csdn.net/wu_huiwen/archive/2010/04/24/5523128.aspx

http://blog.csdn.net/zhuxiaoyang2000/archive/2011/01/17/6147483.aspx

http://blog.csdn.net/zhuxiaoyang2000/category/679833.aspx