Hyperspectral images provide spatial and structural information on samples.This article aims at providing an overview on hyperspectral image analysis research trends, mainly focusing on specific aspects related to this kind of analytical measurement, such as the global/local and the spectral/spatial dualities, the hurdles associated with image fusion strategies, and the design of tools devoted to enhance the spatial definition provided by the instrumental measurement. The complexity of the measurement and the wealth of possibilities to use image properties and information ensure a very lively field of research for the coming years.
| INTRODUCTIONHyperspectral images are beautiful measurements exploiting at the most the spatial and structural information of samples. Images can nowadays focus on the smallest detail (spatial resolutions of nanometer in single-molecule fluorescence images) or on the largest element (pixels covering squared kilometer in remote sensing), and the chemical structure of compounds in a sample can be gathered using almost all imaginable spectroscopies and spectrometries, providing all possible facets from macromolecular to micromolecular structure of the constituents/elements in a sample.Hyperspectral image analysis needs to take into account the spatial/spectral duality, although the research tendency on image analysis has been for a long time to give a larger weight to a particular side of the coin, depending on the field of knowledge and the related applications. Thus, the image processing community has put the accent on the spatial side, whereas classical chemometrics has longer considered hyperspectral images as nothing else than another kind of spectroscopic data set. Such a bias towards space or spectroscopy is not a coincidence. Image processing was born to deal with gray or RGB images, where the small number of channels per pixel (either a gray scale value or 3 color coordinates) did not give much room to exploit information other than the one derived from spatial characteristics, such as textures and edges. On the other hand, chemometrics developed a wide span of multivariate analysis tools focused on interpreting the large amount of high quality structural and chemical information provided by spectroscopic data, and the sole use of this knowledge was often sufficient to give a satisfactory interpretation of the hyperspectral image measurement. Recent research efforts on hyperspectral image analysis point to the development or adaptation of data analysis tools that may benefit from the synergy of using simultaneously properties and information encoded in both spatial and spectral dimensions to improve the final results obtained and take the most of the original measurement.