Detecting image from plain background

I am working on a project in which we need to determine if in the successive frame an image has been placed over the current frame? Also, how can we extract the image?

(As you can see it has to with note-taking applications and so in most of the other frames just some strokes take place)

Any help is really appreciated

[Ahmet Cecen]

Is the first frame ALWAYS identical to the second frame with the exception of the placed image?

OR

Is it always the same image that is being placed on the second frame?

OR

Is the image always placed on the same location?

OR

Do these images being placed share ANY common characteristic at all.