Pattern Comparison

This are actually saved images from different region and different screens. My scenario is that, as the game progresses, I need to save images from different screens and then compare one or two images in order to determine the next action. Please take a look at the algorithm below.

Screen 1, at region1 save img1
Screen 2, at region2 save img2
Screen 3, at region3 save img3
Screen 4, if region4 image is equal to searchImage then
compare img1 to img2
if result is equal then
do this...
elseif not equal
compare img1 to img3
if result is equal then
do other stuff...
else
do that...
end
end