Spatial frequency

In the "Digital Image Processing: Principles and Applications" book, it mentions the following relating to "Spatial frequence":

All images contain details, some fine details and some coarse details. These details are made up of brightness transitions that cycle from dark to light and back to dark. The rate at which brightness cycle is the spatial frequency . The higher the cycle rate, the higher the spatial frequency.

Can you explain this paragraph especially "Cycle rate"? And, if there is an example, this will be much helpful.

Thanks.

[Sean de Wolski]

How is this related to MATLAB?

Answer 1

[Cameron]

spatial frequency is the number of cycles (i.e. transitions between light and dark) per degree of visual angle. Natural images contain spatial frequencies across the range of spatial frequency from the high (e.g. fine details - sharp edges etc) to the low (e.g. coarse details - blobs of light and darkness) end.