| 摘要 |
PURPOSE:To obtain the distinct edge line and trough line which are not influenced by a noise, by adding a differential value of light and darkness to an adjacent picture element, and deciding the light and darkness in accordance with whether this added value is positive or negative, or large or small. CONSTITUTION:A difference before and after delaying a digital video signal inputted from a terminal A, by flip-flop (FF) 21 is derived by an ALU 22, and this difference is added to the previous difference held in a FF 26, by an ALU 25 and recorded in a RAM 27. Also, when codes of the previous difference and the present difference are different, the present difference is stored in the RAM 27. When the processing of a one picture portion is ended, the RAM 27 is read out from the opposite direction, values after and before a delay by an FF 29 are compared by comparators 31, 33, and when the value before the delay is not smaller, and also, its value is larger than a threshold value C1, its value is latched as the maximum value to an FF 40, and thereafter, whether an edge line or a trough line exists in a point having this maximum value or not is decided.
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