| 摘要 |
A method and apparatus to process an electronic image of a document that is previously divided into a plurality of classified tiled rectangular blocks. Each pixel within halftone blocks is analyzed to calculate a busyness measure value, preferably a sum of Laplacians although other range-type functions could be used. When the busyness value is less than a first predetermined threshold value, the video intensity level of the pixel is compared against a second predetermined threshold value and when greater than the second predetermined threshold value, the pixel is re-classified as being a Text document type to produce a crisp, clean background in the rendered image. When the video intensity level of the pixel is less than the second predetermined threshold value, the pixel is re-classified as being a Contone image type to minimize abrupt changes in pixel classification block boundaries, which would result in objectionable artifacts in the rendered image resulting from density or texture changes at the block boundaries. Selectively re-classifying individual pixels within blocks of tiled pixels that were previously classified as halftone pixels greatly reduces rectangular artifacts in the classification map. Such rectangular artifacts in the classification map are often translated by classification driven image processing into undesirable rectangular artifacts when the image is viewed or analyzed further. Certain classification transitions are thereby moved to coincide with contours and transitions in the image video, thereby hiding the classification transitions.
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