| 摘要 |
<p>A method and apparatus for adaptively adjusting (e.g. thresholding) grayscale image data associates with each document image file (210, 212) a predetermined grayscale adjusting function (216) which can be used to threshold, contrast stretch and gray le- vel reduce the original gray level image of the document into a picture representation for display at workstations, the picture re- presentation yielding increased contrast of written and printed text viewed. The invention includes a method of generating a re- mapping function for use in converting near-photographic docu- ment image pixel gray level data lying in a first range of gray level values to higher contrast, background-suppressed pixel gray level data lying in a second more limited gray level range. Global docu- ment information, such as a histogram of all the document's origi- nal pixels, is used to generate at least one threshold gray level va- lue and to determine the shape of the remapping function on either side of the threshold. Preferably, the remapping function is implemented by a look-up table (216) addressed in accordance with the original pixel data.</p> |
