Convergence of the Time Discrete Metamorphosis Model on Hadamard Manifolds

Alexander Effland, Sebastian Neumayer, Martin Rumpf

Research output: Contribution to journalArticle

Abstract

Continuous image morphing is a classical task in image processing. The metamorphosis model proposed by Trouv\'e, Younes, and coworkers [M. I. Miller and L. Younes, Int. J. Comput. Vis., 41 (2001), pp. 61--84; A. Trouv\'e and L. Younes, Found. Comput. Math., 5 (2005), pp. 173--198] casts this problem in the frame of Riemannian geometry and geodesic paths between images. The associated metric in the space of images incorporates dissipation caused by a viscous flow transporting image intensities and its variations along motion paths. In many applications, images are maps from the image domain into a manifold (e.g., in diffusion tensor imaging (DTI), the manifold of symmetric positive definite matrices with a suitable Riemannian metric). In this paper, we propose a generalized metamorphosis model for manifold-valued images, where the range space is a finite-dimensional Hadamard manifold. A corresponding time discrete version was presented in [S. Neumayer, J. Persch, and G. Steidl, SIAM J. Imaging Sci., 11 (2018), pp. 1898--1930] based on the general variational time discretization proposed in [B. Berkels, A. Effland, and M. Rumpf, SIAM J. Imaging Sci., 8 (2015), pp. 1457--1488]. Here, we prove the Mosco--convergence of the time discrete metamorphosis functional to the proposed manifold-valued metamorphosis model, which implies the convergence of time discrete geodesic paths to a geodesic path in the (time continuous) metamorphosis model. In particular, the existence of geodesic paths is established. In particular, the existence of geodesic paths is established. In fact, images as maps into Hadamard manifold are not only relevant in applications, but it is also shown that the joint convexity of the distance function---which characterizes Hadamard manifolds---is a crucial ingredient to establish existence of the metamorphosis model.

Original languageEnglish
Pages (from-to)557-588
Number of pages32
JournalSIAM Journal on Imaging Sciences
Volume13
Issue number2
DOIs
Publication statusPublished - 6 Apr 2020

Keywords

  • Hadamard manifolds
  • Image morphing
  • Manifold-valued images
  • Metamorphosis
  • Shape space
  • Variational time discretization

ASJC Scopus subject areas

  • Applied Mathematics
  • Mathematics(all)

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