| 摘要 |
The invention relates to a system for black/white binary coding of a signal of image elements. According to the invention, it comprises a means (24) for selecting a target image element and image elements around it, a means for detecting a gradation level of each selected image element, a means for determining first and second limits (LB, LW), a means (30) for comparing the gradation level of the target image element with the first limit, for comparing the gradation level of the target image element with the second limit, for coding the target image element at white if its gradation level is higher than the first limit and coding it at black if it is lower than the second limit, a means for calculating a mean gradation level, a means for determining a threshold value according to its mean level and a means for coding the target image element at white if its gradation level is lower than the first limit but higher than the threshold value, and coding it at black if its gradation level is higher than the second limit but lower than the threshold value. The invention applies particularly to facsimiles. <IMAGE>
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