I want to do one of these common experiments to see the effect of increased noise on the performance of a feature detector.
To do this add zero mean gaussian noise with fixed sigma to the image and look at the result. To vary the amount of noise I multiply the noise signal by different amounts before adding.
Since the detector uses a bandpass filter as a first step, to calculate the SNR of the noisy image I calculate the energy of the bandpassed original image, and the energy of the band passed noise signal (before adding them together).
Does this sound reasonable (and is that method of adding noise correct)? My concern is that because the image is being bandpassed, if I evaluate the performance of the detector at a specific point I should be using an SNR value for that local area, rather than the whole image.
How would one go about calculating local signal to noise ratio?