| 摘要 |
PURPOSE:To automatically correct the density of picture data by forming a look up table for converting the density from the upper limit and the lower limit of a histogram and converting a picture having no deviation in the density. CONSTITUTION:A histogram detecting part 2 reads the density (gradation) of the picture data from a picture memory 1 and forms a histogram table 2-1 in which the density is indicated on a horizontal line and a frequency is indicated on a vertical line. A density upper and lower limit detecting part 3 obtains the upper limit density Nj and the lower limit density Nk in which the frequency of the histogram goes to zero. A look up table updating part 4 updates the converting table (look up table 4-1) for converting the upper limit density Nj and the lower limit density Nk to a prescribed density, for instance, a minimum density and an maximum density. The look up table 3-1 is referred with respect to the density of the picture data read from the picture memory 1, it is converted to a desired proper density and displayed on a display 6.
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