You declare your variable image2 as a BinaryImage*, which is why the compiler is having trouble. It sees parameter 1's type as "BinaryImage*", but it is looking for Image*. Also, you don't assign anything out of your call to camera.GetImage(). It should be something like image2 = camera.GetImage() [except that might not be the right type. Check out AxisCamera.h to find out what GetImage() returns].
I don't have the code in front of me, but it is likely that what you need to do is do something like this:
ColorImage colorImage;
camera.getImage(&colorImage);
frcParticleAnalysis(&colorImage, 5, par);
However, we had success last night doing something different. We did something very similar to this. It is unlikely the code below or above will compile, it's coming out of memory.
ColorImage img;
camera.getImage(&img);
BinaryImage* binImg = img.ThresholdRGB(192,256,192,156,192,256);
vector<ParticleAnalysisReport>* particles = binImg->GetOrderedReport(); // I don't remember this function's actual name
for(int x = 0;x < particles.size(); x++)
{
ParticleAnalysisReport& par = (*particles)[x];
// do something with par: look at par.center_mass_x, par.center_mass_y, etc.
}