1. An article-processing device comprising: a conveyor for moving articles in series and on edge, a camera facing transversely relative to the conveyor so as to successively take a digital image of each article, a data processor unit for performing processing on the pixels of the digital image of the article and for inspecting/monitoring the quality of the successive digital images taken by the camera, wherein: said conveyor has a back wall of a dark color and in front of which, relative to the camera, each article passes; said camera is arranged to successively take a digital image of each article within which the article lies against a background corresponding to said back wall of the conveyor, said digital image including both said background and the face of the article; and said data processor unit is arranged to scan rows of pixels in each digital image including pixels corresponding to said back wall in order to extract, for each scanned row, a pixel having a light intensity extremum, said data processor unit further being arranged to extract, from the scanned rows of each successive digital image of an article, a column vector of extrema of level of intensity by scanning all the rows of a digital image, which digital image includes both said back wall and the face of the article, said data processor unit further being arranged to measure said column vector of extrema of level of intensity from each successive digital image over a period of integration of N successive digital images, said data processor unit further being arranged to extract, over said period of integration, a column vector representing the extrema intensity pixels in all of the rows of the column vectors of the successive digital images, said data processor unit further being arranged to detect contrast among successive said extrema intensity pixels, such contrast being indicative of degradation of the quality of the digital images taken by the camera, said data processor unit further being arranged to reinitialize said column vector representing the extrema intensity pixels at each new period of integration of N successive digital images.