Method of effacing zipper image

Abstract

A method of effacing zipper image, applicable to scan a document by a scanner with a stagger charge-coupled device. The nth (n is a positive integer) pixel obtained by scan on a scan line at which the zipper image is produced is subtracted by the (n+1)th pixel obtained by scan on the scan line. The absolute value of the result is then compared to a critical value. If the result is smaller than the critical value, the nth pixel is the nth pixel modified as the nth pixel after process.

1 - 6 . (canceled)  
     
     
         7 . An apparatus comprising: 
 a scanner having a charge-coupled device capable of generating a scan line of pixel values; and    a processing module capable of: 
 determining an absolute value of a difference between an nth pixel value from said scanner in said scan line and an (n+1)th pixel value from said scanner in said scan line; and  
 modifying said nth pixel value in response to said absolute value not exceeding a critical value.  
   
     
     
         8 . The apparatus of  claim 7 , wherein a value of the modified nth pixel substantially equals one half or nearly one half of a sum of the nth pixel value and the (n+1)th pixel value.  
     
     
         9 . The apparatus of  claim 7 , wherein the value of the modified nth pixel substantially equals one half or nearly one half of the nth pixel value plus one half of the (n+1)th pixel value.  
     
     
         10 . The apparatus of  claim 7 , wherein the processing module is capable of determining whether the absolute value is larger than the critical value.  
     
     
         11 . The apparatus of  claim 10 , wherein the processing module is capable of inhibiting modification of said nth pixel value in response to the nth pixel exceeding a critical value.  
     
     
         12 . The apparatus of  claim 7 , wherein the critical value comprises a predetermined value.  
     
     
         13 . The apparatus of  claim 7 , wherein the processing module is adapted to adjust the critical value according to a modulation transfer function.  
     
     
         14 . An apparatus comprising: 
 means for scanning an image;    means for processing the image to obtain pixel values of a scan line;    means for determining an absolute value of a difference between an nth pixel value in said scan line and an (n+1)th pixel value in said scan line; and    means for modifying said nth pixel value in response to said absolute value not exceeding a critical value.    
     
     
         15 . The apparatus of  claim 14 , wherein the modified nth pixel value substantially equals one half or nearly one half of a sum of the nth pixel value and the (n+1)th pixel value.  
     
     
         16 . The apparatus of  claim 14 , wherein the modified nth pixel value substantially equals one half or nearly one half of the nth pixel value added to one half of the (n+1)th pixel value.  
     
     
         17 . The apparatus of  claim 14 , and further comprising means for determining whether the absolute value exceeds the critical value.  
     
     
         18 . The apparatus of  claim 17 , and further comprising means for inhibiting modification of the nth pixel in response to the nth pixel value exceeding the critical value.  
     
     
         19 . The apparatus of  claim 14 , wherein the critical value comprises a predetermined value.  
     
     
         20 . The apparatus of  claim 14 , and further comprising means for adjusting the critical value according to a modulation transfer function.