I hope this isn't too hard a question.
I have a Bitmap object in VB.NET which I drew to using Graphics.DrawImage() (it was a screenshot of the screen which I scaled down. I don't have to scale it down before I process it for changes... whichever way works faster)
Later on, I do the exact same process, and I have a second bitmap object.
Now I need a way to (quickly) determine the basic areas that have changed in the image. Ideally I'd like to know the exact pixels that have changed, but if I, say, could just split the bitmap into some number of conceptual "pieces" and determine if each piece has changed, that's perfect as well.
I can use GetPixel on each and compare the values all the way through the bitmap object... but I imagine it would be painfully slow. I need to do it quickly. Under 50ms preferably for a 1600x1200 size screen o.O I know that's a tall order. I considered maybe comparing every 100th pixel, or comparing down just a few columns and rows, but I don't think it would accurately tell me what areas have changed.
Is there any other way to compare two bitmap objects in VB.NET?