How to compare the two images?

[prakashmaiya]

Dear Expert,

Kindly could any one let me know, that how to compare the two images which captured.

For example, captured the front panel of the car. After few months/year later again capture the front panel of the same car. Just want to compare those two captured images (photo), so that which will gets the differences of two images (might be like some scratch is present in the second image.. just an example).

Along with this only need to compare the object (here object is front panel of the car).

Am doing it for project.

I would really appreciate immediate help. Thanks in advance. :)

Regards,
Maiya

[jefftee]

Unless the two pictures are taken from exactly the same distance, camera angle, and perspective, your task at hand will be very difficult. Even changes in lighting will make detecting differences in the photos tough to do programatically.

This has nothing to do with Qt of course; you may have better luck in a forum dedicated to photo analysis or photo processing.

Edit: a quick google search shows that OpenCV provides the ability to subtract one image from another, which is commonly used to show differences, but the points I made earlier will still apply.