Active shape model

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title: "Active shape model" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["computer-vision"] description: "Statistical model of an object's shape" topic_path: "technology/computing" source: "https://en.wikipedia.org/wiki/Active_shape_model" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Statistical model of an object's shape ::

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.

::figure[src="https://upload.wikimedia.org/wikipedia/commons/1/16/Operation_Of_Shape_Model_In_Active_Shape_Model.jpg" caption="Operation of the shape model"] ::

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.
• 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" method, since it is an analog to an active contour model which would respect explicit shape constraints.

References

References

1. T.F. Cootes and C.J. Taylor and D.H. Cooper and J. Graham. (1995). "Active shape models - their training and application". Computer Vision and Image Understanding.

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::