Active shape model

Active shape models (ASMs) are statistical models of the shape of objects which iteratively deform to fit to an example of the object in a new image, developed by Tim Cootes and Chris J. Taylor in 1995.[1][2][3] The shapes are constrained by the point distribution model (PDM) statistical shape analysis to vary only in ways seen in a training set of labelled examples.

The shape of an object is represented by a set of points (controlled by the shape model). The ASM algorithm aims to match the model to a new image.[4][5][6][7][8]

The ASM works by alternating the following steps:

  • Generate a suggested shape by looking in the image around each point for a better position for the point. This is commonly done using what is called a "profile model", which looks for strong edges or uses the Mahalanobis distance to match a model template for the point.[1]
  • Conform the suggested shape to the point distribution model, commonly called a "shape model" in this context. The figure to the right shows an example.

The technique has been widely used to analyse images of faces, mechanical assemblies and medical images (in 2D and 3D).

It is closely related to the active appearance model. It is also known as a "Smart Snakes"[1] method, since it is an analog to an active contour model which would respect explicit shape constraints.

See also

References

  1. ^ a b c T.F. Cootes; C.J. Taylor; D.H. Cooper; J. Graham (January 1995). "Active Shape Models-Their Training and Application". Computer Vision and Image Understanding. 61 (1): 38–59. doi:10.1006/CVIU.1995.1004. ISSN 1077-3142. Wikidata Q57532916.
  2. ^ T. F. Cootes; G. J. Edwards; C. J. Taylor (1998). "Active appearance models". Lecture Notes in Computer Science: 484–498. doi:10.1007/BFB0054760. ISSN 0302-9743. Wikidata Q29302494.
  3. ^ T.F. Cootes; G.J. Edwards; C.J. Taylor (June 2001). "Active appearance models". IEEE Transactions on Pattern Analysis and Machine Intelligence. 23 (6): 681–685. doi:10.1109/34.927467. ISSN 0162-8828. Wikidata Q30051369.
  4. ^ "Matlab code: open-source ASM implementation". mathworks.com.
  5. ^ "Flexible Models for Computer Vision". isbe.man.ac.uk. Archived from the original on 2006-07-06.
  6. ^ "Tim Cootes home page, one of the original co-inventors of ASMs". personalpages.manchester.ac.uk.
  7. ^ "Source code for ASMs (the "stasm" library)". milbo.users.sonic.net.
  8. ^ "ASMlib-OpenCV, An open source C++/OpenCV implementation of ASM". code.google.com.
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