An active appearance model (AAM) is a
computer vision
Computer vision is an Interdisciplinarity, interdisciplinary scientific field that deals with how computers can gain high-level understanding from digital images or videos. From the perspective of engineering, it seeks to understand and automate t ...
algorithm for matching a
statistical model
A statistical model is a mathematical model that embodies a set of statistical assumptions concerning the generation of sample data (and similar data from a larger population). A statistical model represents, often in considerably idealized form, ...
of object shape and appearance to a new image. They are built during a training phase. A set of images, together with coordinates of landmarks that appear in all of the images, is provided to the training supervisor.
The model was first introduced by Edwards, Cootes and Taylor in the context of face analysis at the 3rd International Conference on Face and Gesture Recognition, 1998. Cootes, Edwards and Taylor further described the approach as a general method in computer vision at the European Conference on Computer Vision in the same year.
The approach is widely used for
matching and tracking faces and for
medical image interpretation.
The algorithm uses the difference between the current estimate of appearance and the target image to drive an
optimization
Mathematical optimization (alternatively spelled ''optimisation'') or mathematical programming is the selection of a best element, with regard to some criterion, from some set of available alternatives. It is generally divided into two subfi ...
process.
By taking advantage of the
least squares
The method of least squares is a standard approach in regression analysis to approximate the solution of overdetermined systems (sets of equations in which there are more equations than unknowns) by minimizing the sum of the squares of the r ...
techniques, it can match to new images very swiftly.
It is related to the
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 Taylor in 1995. The shapes are constrained by the PDM ( point dis ...
(ASM). One disadvantage of ASM is that it only uses shape constraints (together with some information about the image structure near the
landmarks
A landmark is a recognizable natural or artificial feature used for navigation, a feature that stands out from its near environment and is often visible from long distances.
In modern use, the term can also be applied to smaller structures or f ...
), and does not take advantage of all the available information – the texture across the target object. This can be modelled using an AAM.
References
{{Reflist
Some reading
* T. F. Cootes, C. J. Taylor, D. H. Cooper, and J. Graham
Training models of shape from sets of examples ''In Proceedings of BMVC'92, pages 266–275, 1992''
* S. C. Mitchell, J. G. Bosch, B. P. F. Lelieveldt, R. J. van der Geest, J. H. C. Reiber, and M. Sonka
3-d active appearance models: Segmentation of cardiac MR and ultrasound images ''IEEE Trans. Med. Imaging, 21(9):1167–1178, 2002''
* T.F. Cootes, G. J. Edwards, and C. J. Taylor. Active appearance models. ECCV, 2:484–498, 19
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External links
Professor Tim Cootes AAM Code
Free Tools for experimenting with AAMs from Manchester University (for research use only).
Co-creator of AAM page from Manchester University.
IMM AAM Code
Dr Mikkel B. Stegmann's home page of AAM-API, C++ AAM implementation (non-commercial use only).
Matlab AAM Code
Open-source Matlab implementation of the original AAM algorithm.
AAMtools
An Active Appearance Modelling Toolbox in Matlab by Dr George Papandreou.
DeMoLib
AAM Toolbox in C++ by Dr Jason Saragih and Dr Roland Goecke.
Computer vision