if the fucntion of spectrum and psd can be applied on image ?

In matlab , there are two fucntions called spectrum and psd which are showed to estimate PSD, but i can not sure the type of input data. if the fucntion of spectrum and psd can be applied on image ? Thanks!

Answer 1

[Walter Roberson]

The psd() that you are looking at requires a spectrum object to be passed in as the first parameter. The data array, X, that is passed in, will be treated as a discrete time signal. I think that means that each column would be treated as an independent channel, and possibly that only 2D arrays would be supported (not RGB). You might have to pass double() of your image in.

[youjie]

when i applied the psd function on a 2-d matrix(m) and its transposed matrix(m'), i found results were different. I question if this fuction can be used to get PSD of image.

Answer 2

[Image Analyst]

For an image you can call fft2() to get the spectrum. Then take the magnitude and square it. You might also take the log of that, just for display, to compress the lower frequencies so you can see them better.

[youjie]

thanks very much