Preprocessing, images

Although hyperspectral images contain a lot of information, the quality of the raw measurements is often affected by noise or by instrumental variations that hamper the analysis. Typical problems encountered in image measurements are the high noise level, the presence of intense and irregularly shaped baseline contributions or the existence of anomalous pixel spectra (dead pixels or outliers) that may influ- 

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The entire process is detailed in Guezennec et al. (1994) and won t be repeated here. It is important to note that image preprocessing is a necessary step as well as calibration of the geometry because of index of refraction mismatching and lens distortion. It cannot be stressed too much, that accurate calibration and, if possible, as close an index of refraction matching are essential for accurate results. 

Figure 8.1 Image preprocessing of mycelial systems in soil microcosms (a) unprocessed image (b) masking of central inoculum and uncolonised soil area (c) thresholded binary image (d) overlaid grid for box-count determination of fractal dimension (e) close-up of mycelial colonisation of wood resources and localised mycelial patch production (encircled dotted lines).

Rossi M, Segura R, Cierpka C, Kahler CJ (2010) On the effect of particle image intensity and image preprocessing on depth of correlation in micro-PIV. Exp Huids 52 1063-1075. doi 10.1007/s00348-011-1194-z... 

Bow ST. (1992) Pattern Recognition and Image Preprocessing. Marcel Dekker, New York. 

It should be also taken into account that, because of instrumental reasons, the relationship between the spectrum intensity and the concentration may vary from pixel to pixel. Some works recommend specific kinds of image preprocessing to account for these nonchemical differences [52]. 

Thus, in the proposed Combined Preprocessing Method retinal image preprocessing are improved by selecting tiles of two sizes with the aim of obtaining two values of contrast enhancement for each retinal image. 

Image preprocessing is closely related to the experiment, and the choice of an inappropriate instrumental setup or design for data collection may obstruct the automatization of data analysis [9]. 

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