by Bill Green. using the Sobel and the Laplace methods."Edges characterize boundaries and are therefore a problem of fundamental importance in image processing"
a digital signal processing (DSP) technique for identifying frequency components of a signal, published by Dr. Gerald Goertzel in 1958. While the general Fast Fourier transform (FFT) algorithm computes evenly across the bandwidth of the incoming signal, the Goertzel algorithm looks at specific, predetermined frequency.