document: A comparison of computational color constancy algorithms . I : Methodology and experiments with synthesized data We introduce a context for testing computational color constancy , specify our approach to the implementation of a number of the leading algorithms , and report the results of three experiments using synthesized data . Experiments using synthesized data are important because the ground truth is known , possible confounds due to camera characterization and pre-processing are absent , and various factors affecting color constancy can be efficiently investigated because they can be manipulated individually and precisely . The algorithms chosen for close study include two gray world methods , a limiting case of a version of the Retinex method , a number of variants of Forsyth 's -LRB- 1990 -RRB- gamut-mapping method , Cardei et al. 's -LRB- 2000 -RRB- neural net method , and Finlayson et al. 's color by correlation method -LRB- Finlayson et al. 1997 , 2001 ; Hubel and Finlayson 2000 -RRB- . We investigate the ability of these algorithms to make estimates of three different color constancy quantities : the chromaticity of the scene illuminant , the overall magnitude of that illuminant , and a corrected , illumination invariant , image . We consider algorithm performance as a function of the number of surfaces in scenes generated from reflectance spectra , the relative effect on the algorithms of added specularities , and the effect of subsequent clipping of the data . All data is available on-line at http://www.cs.sfu.ca/~color/data , and implementations for most of the algorithms are also available -LRB- http://www.cs.sfu.ca/~color/code -RRB-
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