Image comparison algorithm

Question

I\'m trying to compare images to each other to find out whether they are different. First I tried to make a Pearson correleation of the RGB values, which works also quite go

Answer 1

I guess you could do something like this:

• estimate vertical / horizontal displacement of reference image vs the comparison image. a simple SAD (sum of absolute difference) with motion vectors would do to.

• shift the comparison image accordingly

• compute the pearson correlation you were trying to do

Shift measurement is not difficult.

• Take a region (say about 32x32) in comparison image.
• Shift it by x pixels in horizontal and y pixels in vertical direction.
• Compute the SAD (sum of absolute difference) w.r.t. original image
• Do this for several values of x and y in a small range (-10, +10)
• Find the place where the difference is minimum
• Pick that value as the shift motion vector

Note:

If the SAD is coming very high for all values of x and y then you can anyway assume that the images are highly dissimilar and shift measurement is not necessary.