In this chapter, we will introduce the application of HMM in the case of image segmentation. For image segmentation, we usually split up the given image into multiple blocks of equal size and then perform an estimation for each of these blocks. However, these algorithms usually ignore the contextual information from the neighboring blocks. To deal with that issue, 2D HMMs were introduced, which consider feature vectors to be dependent through an underlying 2D Markovian mesh. In this chapter, we will discuss how these 2D HMMs work and will derive parameter estimation algorithms for them. In this chapter, we will discuss the following topics:
- Pseudo 2D HMMs
- Introduction to 2D HMMs
- Parameter learning in 2D HMMs
- Applications