Extracting Edges from Images

Many edge extraction techniques can be broken up into two distinct phases:

• Finding pixels in the image where edges are likely to occur by looking for discontinuities in gradients.

  Candidate points for edges in the image are usually referred to as edge points, edge pixels, or edgels.
  

• Linking these edge points in some way to produce descriptions of edges in terms of lines, curves etc.

Each phase in turn will be discussed in the following Sections.