How can I tell if an image is part of another image? I have one image that may or may not be part of another image (possibly resized).

How can I tell if that's the case, and pointing out the region of the first image that contains the second?
For example, I'd like to tell that the second image is an enlarged portion of the first.
This problem can be treated as signal/image detection or image registration. From the image registration perspective, there is a good tutorial that is exactly what you need: Registering an Image Using Normalized Cross-Correlation