Resources for learning image processing
Gonzales&amp;Woods is a good book. 

since u need some other book for reference i may suggest 
 
Author: S. Jayaraman, S. Esakkirajan And T. Veerakumar
 
Title of the Book: Digital Image Processing
 
Publisher: Tata McGraw - Hill Education Pvt. Ltd, New Delhi
 
Year: 2010
 
Edition: 3

This is also good book for beginners