Lots of folks have suggested methods for developing an algorithm so I'll point you to some software that is free and very powerful. ImageJ is funded by the National Institutes of health, it is freely available and more than capable of the degree of image analysis you'll require. As others have mentioned image quality and consistency can be a huge hurdle so make life easier by setting everything up with care.
Slashdot Mirror
Lots of folks have suggested methods for developing an algorithm so I'll point you to some software that is free and very powerful. ImageJ is funded by the National Institutes of health, it is freely available and more than capable of the degree of image analysis you'll require. As others have mentioned image quality and consistency can be a huge hurdle so make life easier by setting everything up with care.