| 摘要 |
PURPOSE:To obtain an excellent pseudo intermediate tone reproduced picture even with all original at a low constrast and with a fluorescent tube whose service life is close to expiration by obtaining an accumulated density function so as to generate a dither matrix in matching with the tendency of contrast of the original. CONSTITUTION:When an original is set to an original read section 3, the original read section 3 starts the photoelectric conversion of the original and applies A/D conversion. The quantized picture data is sent to a counter 7, where the frequency of occurrence for each brightness level is accumulated, the arithmetic section 9 normalizes the frequency to calculate the accumulated density function CDF. The arithmetic section 9 cuts off the part above and below 5% of the brightness range of the said function CDF, divides the brightness range of CDF 0.05-0.95 by a matrix number (e.g., 16), obtains the threshold value of 16-stage to generate the dither matrix. Then all the originals are read to generate a pseudo intermediate tone data.
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