| 摘要 |
PURPOSE:To restrain only a grounding or a part thinner than the density of the grounding in a popied picture from being copied, or to copy them by the prescribed density by detecting the density of the grounding of the original picture, and converting the grounding and the part thinner than the density of the grounding into the prescribed density. CONSTITUTION:Signals R, G, B outputted from a photoelectric converting element array 1 by the scanning of an optical system unit are supplied to a memory 6 through an A/D converter 2, and a histogram to show the frequency distribution of color density in the original picture is generated by a CPU 7. This histogram shows high frequency at the density near to white of the grounding of the original, and a conversion table is written in a circuit 3 as referring to a threshold, and the signals R, G, B are converted into the signals R', G', B' according to a conversion function, and are inputted to a density conversion circuit 4. The circuit 4 converts the inputted signals into the density signals C', M', Y', and further, color correction processing is performed by a color correction circuit 5, and the signals of C'', M'', Y'', Bk'' corresponding to cyan, magenta, yellow and black are outputted. Thus, only the grounding or the part thinner than the grounding density of the copied picture can be copied by the prescribed density. |
