detecting changes between two images (detecting appearances of new objects)

Question

This is my first question on Stackoverflow, so at first - hi everyone :)

I'm a newbie in image processing, but I have to write an app (in Java) to detect changes between images from a camera (or rather to detect new objects on images). A camera is taking a picture every minute, all day, so as an input I have a sequence of color images in JPG. The important things are:

1. the camera isn't moving, so a background doesn't change. I'm interested only in detecting objects (e.g. people, animals, cars, ..) between lens and a background
2. it should be impervious to image noise from a camera or weather (e.g. rain, snow, sun moving - shades)
3. the only thing I need as an output is an information that sth has changed between two images

I'm interested in as simple solution as possible, but it has to be a working solution. It doesn't need to be infallible, but it should work correctly in most normal cases.

Of course, I don't expect someone give me a ready to use snippet of a code (although that would be great! ;) ), but if someone, who knows the topic, gives me some guidelines (steps to do, algorithms or articles to read), I'll be really gratefull. I haven't found nothing appropriate on google and unfortunately I don't have a year to read few books and do a PhD to find a solution :)

Answer 1

As a simple solution, just subtract one image from the other and look at the differences. Ignore small changes and try to build area of movement and just accept bigger areas.

Answer 2

1. you can parse md5 of the image and compare parts of it, and check if they are similar or not, you can refer to this

2. You can use Keypoint Matching which is almost the same method as 1 you can read about this.

3. Read about Histogram method