This chapter presents the following content: Image understanding, define the image objects representation mechanism, use of the segmentation, representations, boundary based segmentation, region based segmentation, description, boundary based segmentation, region based segmentation. | Digital Image Processing CSC331 Object Representation 1 Summery of previous lecture Morphological image processing Morphological operations Dilation and Erosion Morphological closing Morphological opening Hit and Miss transform Boundary extraction Region filling Extraction of connected component Thinning Thickening Skeletonization 2 Todays lecture image understanding Define the Image objects representation mechanism Use of the segmentation representations boundary based segmentation region based segmentation Description boundary based segmentation region based segmentation 3 Representation and Description A segmented region can be represented by boundary pixels internal pixels When shape is important, a boundary (external) representation is used When colour or texture is important, an internal representation is used The description of a region is based on its representation, for example a boundary can be described by its length The features selected as descriptors are usually required to be as insensitive as possible to variations in (1) scale, (2) translation and (3) rotation 4 Representation Image data, for example a boundary, is usually represented in a more compact way so that it can be described more easily Skeletonization, that is the process that reduces the boundary of a region to a graph (which is a single pixel thick), often pre- cedes other representation schemes and is therefore discussed first 5 Chain Codes Assumption: thinning algorithm already applied to edge pixels Generation of chain code: follow the boundary in an anti-clockwise direction and assign a direction to the segment between successive Difficulties: Noise changes the code pixels Code generally very long Solution: Resample the boundary using a larger grid spacing New boundary represented by 4- or 8-directional chain code 6 Chain codes: represent a boundary of a connected region and its moves are define 7 Representation Chain Codes Chain code depends on starting point Chain code is . | Digital Image Processing CSC331 Object Representation 1 Summery of previous lecture Morphological image processing Morphological operations Dilation and Erosion Morphological closing Morphological opening Hit and Miss transform Boundary extraction Region filling Extraction of connected component Thinning Thickening Skeletonization 2 Todays lecture image understanding Define the Image objects representation mechanism Use of the segmentation representations boundary based segmentation region based segmentation Description boundary based segmentation region based segmentation 3 Representation and Description A segmented region can be represented by boundary pixels internal pixels When shape is important, a boundary (external) representation is used When colour or texture is important, an internal representation is used The description of a region is based on its representation, for example a boundary can be described by its length The features selected as descriptors are usually required
