confusion of Frequency domain in image processing

[syedshan]

Hi all

I have a question in understanding the frequency thing in image or pixel. I am confused particularly about the frequency of image or pixel in the quote below. Can anyone let me understand

Edge pixels generally correspond to high-frequency components and interior pixels of an object region correspond to low-frequency components.

 

[D.A.(Tony)Stewart]

The frequency is related to rate of change of contrast, the toggle rate relative to the pixel frequency.