检查位图是否已被修改

Question

I have a class that wraps around a Bitmap and I would like to have a way of knowing if the bitmap has been changed (via SetPixel or GDI+).

I don't need to know exactly when it happens, I just need a way to tell if it has happened since the last check.

Now, I'm assuming that something like that isn't already packed in the Bitmap class, so what would be the best way to solve this problem?

I could provide my own wrapper functions for GetPixel and SetPixel, but then I'd have no idea if the Bitmap was changed using GDI. I COULD make a wrapper for that too but that really seems like a huge overkill.

Another possible option would be to save a copy and then check pixel by pixel. This would obviously work and would be trivial to write but it's much too slow for my needs.

Answer 1

You should use a hash or check sum. There are some easy ways to do this but I think the simplest way would be to have a string hash property in your class then call GetHashCode() on the bitmap/binary string/whatever container you're storing it in. Set it to the classes property, check the current hashcode against that value to see if anything has changed. You could also write your own little checksum function or choose from (I'm sure) a vast array of third party options.