Here’s a graphical illustration of the difference between CENTER_INSIDE and FIT_CENTER.

Image used (100 × 100):

Small image view (75 × 50):

CENTER_INSIDE:

FIT_CENTER:

Both CENTER_INSIDE and FIT_CENTER shrink the image.

Large image view (300 × 200):

CENTER_INSIDE:

FIT_CENTER:

CENTER_INSIDE does not enlarge the image, FIT_CENTER does.

_{The Android robot is reproduced or modified from work created and shared by Google and used according to terms described in the Creative Commons 3.0 Attribution License.}