| 摘要 |
PCT No. PCT/SE96/00347 Sec. 371 Date Sep. 17, 1997 Sec. 102(e) Date Sep. 17, 1997 PCT Filed Mar. 19, 1996 PCT Pub. No. WO96/29676 PCT Pub. Date Sep. 26, 1996According to the invention there is provided a method for transforming a gray-level image, divided into pixels, into a black-and-white image, comprising the steps of: dividing the gray-level image into a number of generally square sub images which comprise more than one pixel; calculating and storing, for each sub image, at least one measurement value representing the gray-level of the sub image; calculating, for each sub image, a threshold value based on the measurement values of the sub image, and a number of sub images that are adjacent the sub image; and transforming, for each sub image, each pixel in the sub image to either a white or a black pixel depending upon whether the gray-level of the pixel exceeds the threshold value of the sub image or not. Preferably, parts of the gray-level image, the measurement value or values that is/are calculated, for each sub image, and the threshold value that is calculated, for each sub image, are temporarily stored in one or more memory buffers. These data are stored only as long as they are needed for calculation and/or transformation and are then written over by new data. |
