Local trilateral upsampling for thermal image

This paper presents an image upsampling method. Joint-bilateral filtering has been successfully applied to this problem that upsample “target” images using high-resolutional “control” images. In this filtering, the kernel is a product of weights representing spatial proximity and color (or intensity) proximity of the “control” image. However, when the “target” image involves textures that are invisible in the “control” image, these textures are damaged by this upsampling. In the case of thermal target image and visible-light control image, we can often find such textures. For solving this problem, we first propose trilateral upsampling, which is a simple extension of joint-bilateral upsampling incorporating color (or intensity) proximity weight in the “target” image. For improving this method so as to increase the spatial resolution, we introduce weight control based on local mutual information between target and control images. We confirmed that resulted images have higher spatial resolution and lower noise.