[a,M,L,N,Ngood]=gabimagepars(Ls,x,y);
[a,M,L,N,Ngood]=gabimagepars(Ls,x,y) will compute a reasonable set of parameters a, M and L to produce a nice Gabor 'image' of a signal of length Ls. The approximate number of pixels in the time direction is given as x and the number of pixels in the frequency direction is given as y.
The output parameter Ngood contains the number of time steps (columns in the coefficients matrix) that contains relevant information. The columns from Ngood until N only contains information from a zero-extension of the signal.
If you use this function to calculate a grid size for analysis of a real-valued signal (using dgtreal), please input twice of the desired size y. This is because dgtreal only returns half as many coefficients in the frequency direction as dgt.
An example: We wish to compute a Gabor image of a real valued signal f of length \(7500\). The image should have an approximate resolution of \(600 \times 800\) pixels:
[f,fs]=linus; f=f(4001:4000+7500); [a,M,L,N,Ngood] = gabimagepars(7500,800,2*600); c = dgtreal(f,'gauss',a,M); plotdgtreal(c,a,M,fs,90);
The size of c is \((M/2)+1 \times N\) equal to \(601 \times 700\) pixels.
For this function to work properly, the specified numbers for x and y must not be large prime numbers.