In most applications edges and lines in images carry more useful information than other types of features such as texture, color, etc. Edges and lines may be caused by various reasons:
Edge detection is one of the most essential tasks in image processing. As edges and lines are drastic changes in gray level over a small spatial distance, they correspond to high spatial frequency components in the image signal. The main challenge is to distinguish edges from other small features in the image such as textures and especially the noise, so that all edges are detected while the noise is suppressed.
Human vision is very good at edge detection. You can easily detect the edges in this image. But it may be very challenging to detect these edges by a computer. The difficulty of edge detection can be best appreciated by looking at the profile of the image shown on the top part of the image.
