You could start by looking at some of the similar questions on this site:
- where-do-i-start-learning-about-image-processing-and-object-recognition
- image-processing-textbook
- computer-vision-reference
I can also look at these two sites:
- http://www.cs.cmu.edu/afs/cs/project/cil/ftp/html/vision.html
- http://www.cs.cf.ac.uk/Dave/Vision_lecture/Vision_lecture_caller.html
The sites provide information, tutorials and code examples, even though they are not actively maintained anymore.
