Phase congruency is a measure of feature significance in computer images, a method of edge detection that is particularly robust against changes in illumination and contrast.
Phase congruency reflects the behaviour of the image in the frequency domain.
This corresponds to the human-perceived edges in an image where there are sharp changes between light and dark.
Phase congruency compares the weighted alignment of the Fourier components of a signal
[3] The square-wave example is naive in that most edge detection methods deal with it equally well.
A notable example is an image feature consisting of a single line, such as the letter "l".