A special case of the more general concept of an immutable object - an object that cannot be modified after it is created.

For the case of an immutable image, you can read the image but not change it.

An immutable object is classed in Java programming as an object that cannot be changed after it is made. YouTube has videos that can be viewed on this subject as well as Vimeo.

unchangeable, never changing. Immutable object is an object whose state cannot be modified after it is created

lmutable object

A field that doesn't change is informally called "constant," or more formally "immutable." This is in contrast to fields that can change with are called "mutable." The main importance Mutability is in multi-threaded programs, where the program can be executing in multiple places at once. A common multi-threading bug is one thread using a mutable object while another thread changes it without realizing the first thread is still using the object. A solution is to make the object immutable and create a new immutable object when the values change. That way threads may get different objects but they can count on them not to change.

Python does not have a way to guarantee an arbitrary object is immutable. You have to enforce it by programming practice. Python does have an immutable list called a "tuple."