A Survey on Breaking Technique of Text-Based CAPTCHA

Table 7

Comparisons of segmentation methods.

Segmentation methods	Main basis	Character features				Explanation
		Adhesion	Skew	Distortion	Overlap
Segmentation based on individual character	Character projection	√	×	×	×	Suit strings with little adhesion rather than serious distorted, overlapped strings
	Connected components	×	√	√	×	Limited to overlapping rather than distortion
	Character width	√	×	×	×	Limited to severely distorted
	Character feature	√	×	×	×	Effective when character feature is notable and discriminant
	Character contour	√	√	√	×	Applied to the individual character with clear contour
Segmentation base on character components	Character structure	√	√	√	√	Only when character structure is easy to segment
	Filter	√	√	√	√	Wide application; the subsequent processing is complex