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SUMMARY:Shape modelling using contours and fields\, with applications to i
 mage segmentation - Ian Jermyn (Durham)
DTSTART:20151106T160000Z
DTEND:20151106T170000Z
UID:TALK60701@talks.cam.ac.uk
CONTACT:Quentin Berthet
DESCRIPTION:Images play many vital roles today: satellite images in enviro
 nmental and climate studies\; MRI imagery in medicine\; microscope images 
 in cell biology. Increasing data volume means that the automatic extractio
 n of information from these images is essential if the potential of the da
 ta is to be realized. Many of the key problems involve shape\, for example
  `segmentation': the delineation of a specified entity in the image. Shape
  modelling is thus a crucial ingredient of automatic inference methods.\n\
 nFor the most part\, work has focused on families of shapes consisting of 
 perturbations of a given reference shape with a simple topology. There are
  applications\, however\, where the family of shapes involved does not hav
 e such a constrained behaviour. Cases where the number of individual objec
 ts is unknown a priori\, or where the topology of the shape may be otherwi
 se complex (for example network shapes)\, require new techniques.\n\nI wil
 l begin by describing the 'higher-order active contour' (HOAC) framework. 
 By introducing explicit long-range interactions between shape boundary poi
 nts\, HOACs can model families of shapes sharing geometric properties with
 out overly constraining topology. The representation of complex shapes by 
 their boundaries is\, however\, often inconvenient\, despite its intuitive
  nature. The alternative\, 'phase field' representation offers a number of
  advantages without loss of expressive power. In particular\, phase field 
 equivalents of HOACs can be constructed. Phase fields also facilitate the 
 translation of models to a third useful representation\, binary Markov ran
 dom fields\, simplifying sampling and annealing.\n\nI will present several
  models developed within this framework\, in particular models of network 
 shapes and of a 'gas of near-circles'\, and will describe applications to 
 the segmentation of road networks and tree crowns from satellite and aeria
 l images\, and cells from microscopic images.
LOCATION:MR12\, Centre for Mathematical Sciences\, Wilberforce Road\, Camb
 ridge.
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