I can only second this. Gonzalez & Woods presents a very good overview of the material in a highly practical and understandable way. Each section contains tons of references into the more specific literature that you can follow as soon as you reached the books limits. Finally, it is a pleasure to read if you are interested in image processing and it keeps you hooked.

If you want a smaller and cheaper book on computer vision, I recommend Concise Computer Vision (Klette, Springer).

It's remarkably complete for its size. The level of detail is just enough that you can refresh or understand a topic, without drowning you in equations. The referencing could be better, but the main papers are called out.

By chance, do you know a good book for audio signal processing?

For signals (as opposed to images), you should have a look at "Understanding Digital Signal Processing" by Richard G. Lyons (ISBN-13: 978-0131089891). I enjoyed this very much and if you grasped the contents from it, you should be able to understand audio-specific books easily.

I second Lyons. In addition, "Digital Signal Processing: A Practical Guide" by Steven Smith is also quite approachable -- immersion in calculus not required.

"A Digital Signal Processing Primer" by Ken Steiglitz is a nice but rigorous intro to the subject. Written by an EE academic, it's more mathematically rigorous than Smith or Lyons.

Allen Downey's "Think DSP" is also worth a look, though its focus is more conceptual than practical, IMO.

DAFX by Zölzer covers all the fundamental audio DSP building blocks. The book is eponymous with the annual international audio DSP conference.

Yes, I should have included this in my post, it's another perfect example of bringing the theoretical to the real world view.