55:148 Digital Image Processing
55:247 Image Analysis and Understanding

Chapter 13,
Texture: Syntactic texture description

• Syntactic texture description approaches are not used as widely as statistical ones.
• Syntactic texture recognition - analogy between texture spatial relationships and structure of a formal language.
• Textures from one class form a language represented by its grammar.
• Recognition process is a syntactic analysis of the texture description word.

• Purely syntactic texture description models are based on idea of almost regular spatial organization of texture primitives.
• Grammar representation - primitives are terminal symbols, relationships are represented as transformation rules.
• Grammar is a very strict formula but real-world textures are frequently irregular - this causes problems.
• Grammar description of textures used more often for texture synthesis.

• Syntactic texture description in reality requires variable rules, and use of non-deterministic grammars.

• chain grammars are the simplest grammars usable for texture description
• start symbol --> shape rules

• Example of hexagonal texture generation:

• Texture analysis ...
• texture a) will be accepted as generated by the above grammar
• texture b) will be rejected

Graph grammars

• description using planar graphs

Primitive grouping in hierarchical textures

• Several levels of primitives can be detected in hierarchical textures
• lower level primitives may form a specific pattern which can be considered a primitive at a higher description level

• Primitive grouping detects the hierarchically higher level units in the texture
• Several levels of hierarchies may occur so grouping has to continue until no more grouping is possible

• Grouping plays the same role as feature description in statistical methods - different primitives and/or different spatial relationships represent different textures
• In the figure above, textures can be distinguished as consisting of different primitives after the grouping step