| 摘要 |
PURPOSE:To obtain a sharp binary image even from an input picture to which an object and its background are almost at the same light level by sequentially varying a threshold with changes in the video level of an input signal. CONSTITUTION:A comparator 7 compares the levels of signals outputted from a video processor 4. If a video signal goes to a high value, by the effect of a reversal attenuator 5, the threshold may be and a binarization signal may be set to a high level. As a result the light part of an image is emphasized. Conversely, if the video signal goes to a low value, the threshold is increased to emphasize the dark part of the image. Thus, even if the difference between the object and the background is not clear, a precise binarization can be made with the aid of the threshold by using a difference when the difference of some extent exists. Based on this the principle, the comparator 7 compares the levels, and outputs the high level signal if the video signal is higher than the threshold, otherwise, it outputs the low level signal.
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