Method and filtering system for filtering edge directions

Abstract

A filtering method and filtering system is applied to an edge orientation map obtained from an edge direction detection system in order to keep accurate edge directions and filter out false edges or edges with wrong directions. If an edge direction does not have a certain minimum length, then that direction is filtered out and a default direction is provided. Additional assurances can be obtained by insuring that the edge direction has a certain minimum width. If an edge direction does not have the minimum width, then that edge direction is filtered out and the default direction is provided. A direction smoother can be applied to the directions in the edge orientation map to smooth the changing of neighboring edge directions. This process is found to be effective in improving the visual quality of an image that is interpolated based on edge directions.

1 - 12 . (Canceled).  
   
   
       13 . An edge direction filtering system, comprising: 
 a direction filter that extends a current edge direction to neighboring rows in an edge orientation map;    said direction filter further determines an orientation similarity between the current edge direction and neighboring edge directions located along the current edge direction;    wherein the direction filter indicates if the current edge direction is valid.    
   
   
       14 . The system of  claim 13  wherein the direction filter determines if the current edge direction is valid by determining if the current edge direction can be extended to a certain number of neighboring rows in the edge orientation map.  
   
   
       15 . The system of  claim 13  wherein the direction filer extends the current edge direction to neighboring upper and lower rows in the edge direction map.  
   
   
       16 . The system of  claim 15  wherein the direction filter determines if the current edge direction is valid by determining if the current edge direction can be extended to a certain number of neighboring rows in the edge orientation map.  
   
   
       17 . The system of  claim 13  wherein the direction filter further extends the current edge direction in the same row as the current edge direction in the edge direction map.  
   
   
       18 . The system of  claim 17  wherein the direction filter determines if the current edge direction is valid by determining if the current edge direction can be extended to a certain number of neighboring rows in the edge orientation map.  
   
   
       19 . The system of  claim 13  wherein the direction filter extends the current edge direction in the same row as the current edge direction in the edge direction map, wherein the direction filter checks an orientation similarity between the current edge direction and neighboring edge directions on a row with the current edge direction in the edge orientation map, whereby the direction filter indicates that the current edge direction is valid if a certain number of consecutive ones of the neighboring edge directions on the row with the current edge direction have a similar orientation to the current edge direction.  
   
   
       20 . The system of  claim 13  further comprising a low pass filter for smoothing transitions between neighboring edge directions of the edge orientation map.  
   
   
       21 . A method for filtering edge directions, comprising the steps of: 
 extending a current edge direction to neighboring rows in an edge orientation map;    determining an orientation similarity between the current edge direction and neighboring edge directions located along the current edge direction; and    indicating if the current edge direction is valid.    
   
   
       22 . The method of  claim 21  wherein the step of extending the current edge direction further includes the steps of determining if the current edge direction is valid by determining if the current edge direction can be extended to a certain number of neighboring rows in the edge orientation map.  
   
   
       23 . The method of  claim 21  further including the steps of extending the current edge direction to neighboring upper and lower rows in the edge direction map.  
   
   
       24 . The method of  claim 23  further including the steps of determining if the current edge direction is valid by determining if the current edge direction can be extended to a certain number of neighboring rows in the edge orientation map.  
   
   
       25 . The method of  claim 21  further including the steps of extending the current edge direction in the same row as the current edge direction in the edge direction map.  
   
   
       26 . The method of  claim 25  further including the steps of determining if the current edge direction is valid by determining if the current edge direction can be extended to a certain number of neighboring rows in the edge orientation map.  
   
   
       27 . The method of  claim 21  further including the steps of extending the current edge direction in the same row as the current edge direction in the edge direction map, and checking an orientation similarity between the current edge direction and neighboring edge directions on a row with the current edge direction in the edge orientation map, to indicate that the current edge direction is valid if a certain number of consecutive ones of the neighboring edge directions on the row with the current edge direction have a similar orientation to the current edge direction.  
   
   
       28 . The method of  claim 21  further including the steps of applying a low pass filter for smoothing transitions between neighboring edge directions of the edge orientation map.