| 摘要 |
PURPOSE:To form a half tone picture without a deterioration in gradation reproducibility even by using a small matrix by correcting the variable density value of a picture element at a current scanning position according to the weighted averaged value of an error between the variable density value of an input and the variable density value of an output. CONSTITUTION:The variable density value of data from a picture input device 1 or a picture memory 2 is converted to the area of the picture element by a picture processor 3. The error between the variable density value of the input and the variable density value of the output is operated for every picture element of an input picture and this error is stored in an error buffer disposed in the picture buffer processor 3. The error of the three picture elements in the vicinity of the two dimension of a scanning picture element is multiplied by a weight coefficient and summed up and it is defined to be the quantity of ER of the error to be corrected by the scanning picture. Then, the quantity ER of the error is subtracted from the variable density value of the current scanning picture element to obtain the final variable density value after the correction, this final variable density value is compared with a preset threshold matrix to obtain an output pattern. Thereby, the half tone picture in which the error as the average is corrected can be obtained.
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