Text/continuous tone image decision processor

摘要

Grayscale image data obtained by scanning a document to be duplicated is partitioned into contiguous image data blocks which are processed to determine whether the portions of the image represented by the data blocks correspond to text or continuous tone portions of the document. An average grayscale value is determined for each data block and used as an indexing variable for at least one additional characteristic determined for the block. Disclosed additional characteristics include a block variance, a block edge count, a block agreement count and a block text average. A one dimensional Gaussian distribution is generated to distribute the data values of any additional characteristics for each possible grayscale value of a block. The mean and standard deviation are determined for each data distribution and the Mahalanobis distance for each characteristic data value is determined. The Mahalanobis distance is a representative probability for whether the image data block corresponds to a text portion of the image or a continuous tone portion of the image.