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Active shape models (ASMs) are
/ref> The shapes are constrained by the PDM ( point distribution model) Statistical Shape Model 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.
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
Matlab code
open-source ASM implementation.
of AAMs from Manchester University.
Tim Cootes'
home page (one of the original co-inventors of ASMs).
Source code
for ASMs (the "stasm" library).
ASMlib-OpenCV
An open source C++/OpenCV implementation of ASM. {{DEFAULTSORT:Active Shape Model Computer vision
statistical model
A statistical model is a mathematical model that embodies a set of statistical assumptions concerning the generation of Sample (statistics), sample data (and similar data from a larger Statistical population, population). A statistical model repre ...
s of the shape
A shape is a graphics, graphical representation of an object's form or its external boundary, outline, or external Surface (mathematics), surface. It is distinct from other object properties, such as color, Surface texture, texture, or material ...
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./ref> The shapes are constrained by the PDM ( point distribution model) Statistical Shape Model 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.
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
The Mahalanobis distance is a distance measure, measure of the distance between a point P and a probability distribution D, introduced by Prasanta Chandra Mahalanobis, P. C. Mahalanobis in 1936. The mathematical details of Mahalanobis distance ...
to match a model template for the point.
* 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 An active appearance model (AAM) is a computer vision algorithm for matching a statistical model 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 appe ...
. It is also known as a "Smart Snakes" method, since it is an analog to an active contour model which would respect explicit shape constraints.
See also
*Procrustes analysis
In statistics, Procrustes analysis is a form of statistical shape analysis used to analyse the distribution of a set of shapes. The name '' Procrustes'' () refers to a bandit from Greek mythology who made his victims fit his bed either by stretch ...
* Point distribution model
References
External links
Matlab code
open-source ASM implementation.
of AAMs from Manchester University.
Tim Cootes'
home page (one of the original co-inventors of ASMs).
Source code
for ASMs (the "stasm" library).
ASMlib-OpenCV
An open source C++/OpenCV implementation of ASM. {{DEFAULTSORT:Active Shape Model Computer vision