Computer program for generating 1-bit image data from multiple-bit image data

Abstract

A computer program for, or method of, generating 1-bit image data from multiple-bit image data, by a process which comprises the steps of: receiving multiple-bit image data comprising multiple-bit pixel values; and deriving from the multiple-bit pixel values 1-bit image data comprising “on” and “off pixel values, each pixel value of the 1-bit image data corresponding to a pixel of an output medium, which pixel an output device would attempt to mark when printing the 1-bit image data if the pixel value were “on”, the 1-bit image data producing when printed an image constituted by dots, each dot corresponding to a plurality of pixel values of the 1-bit image data, which pixel values correspond to a block of M*N horizontally and/or vertically adjacent pixels of an output is medium, at least one of M and N being greater than one, wherein for at least some of the dots, where M or N is equal to one, a pixel value corresponding to a first or last pixel of a row of horizontally adjacent pixels, or to a first or last pixel of a column of vertically adjacent pixels, is “off, and where both M and N are greater than one, at least one pixel value corresponding to a pixel of a first or last row of horizontally adjacent pixels is “off and/or at least one pixel value 20 corresponding to a pixel of a first or last column of vertically adjacent pixels is “off.

The invention claimed is: 
     
       1. A computer system executed process for generating 1-bit image data from multiple-bit image data, the process comprising the steps of:
 receiving, by the computer system, multiple-bit image data comprising multiple-bit pixel values; and 
 deriving, by the computer system, from the multiple-bit pixel values 1-bit image data comprising “on” and “off” pixel values, each pixel value of the 1-bit image data corresponding to a pixel of an output medium, which pixel an output device would attempt to mark when printing the 1-bit image data if the pixel value were “on”, the 1-bit image data producing when printed an image constituted by dots, each dot corresponding to a plurality of pixel values of the 1-bit image data, which pixel values correspond to a block of M*N horizontally and/or vertically adjacent pixels of an output medium, at least one of M and N being greater than one, wherein for at least some of the dots, where M or N is equal to one, a pixel value corresponding to a first or last pixel of a row of horizontally adjacent pixels, or to a first or last pixel of a column of vertically adjacent pixels, is “off”, and where both M and N are greater than one, at least one pixel value corresponding to a pixel of a first or last row of horizontally adjacent pixels is “off” and/or at least one pixel value corresponding to a pixel of a first or last column of vertically adjacent pixels is “off”. 
 
     
     
       2. The process of  claim 1 , wherein the 1-bit image data produce when printed an image constituted by a plurality of densities of dots. 
     
     
       3. The process of  claim 1 , wherein both of M and N are greater than one, and for at least some of the dots, at least one pixel value corresponding to a pixel of at least one of first and last rows of horizontally adjacent pixels of the block is “off” and at least one pixel value corresponding to a pixel of at least one of first and last columns of vertically adjacent pixels of the block is “off”. 
     
     
       4. The process of  claim 3 , wherein for at least some of the dots, the pixel values corresponding to the pixels of at least one of first and last rows of horizontally adjacent pixels and at least one of first and last columns of vertically adjacent pixels are “off”. 
     
     
       5. The process of  claim 1 , wherein for densities of dots greater than a first threshold density, where M or N is equal to one, a pixel value corresponding to a first or last pixel of a row of horizontally adjacent pixels, or to a first or last pixel of a column of vertically adjacent pixels, is “off”, and where M and N are both greater than one, at least one pixel value corresponding to a pixel of a first or last row of horizontally adjacent pixels is “off” and/or at least one pixel value corresponding to a pixel of a first or last column of vertically adjacent pixels is “off”. 
     
     
       6. The process of  claim 5 , wherein M and N are both greater than one and for densities of dots less than a second threshold density, pixel values corresponding to pixels that, if unmarked, would separate horizontally or vertically adjacent dots, are “on”, the second threshold density being greater than the first threshold density. 
     
     
       7. The process of  claim 6 , wherein for densities of dots less than a third threshold density, at least one pixel value corresponding to a pixel that, if unmarked, would separate horizontally or vertically adjacent dots, is “off”, the third threshold density being greater than the second threshold density. 
     
     
       8. The process of  claim 7 , wherein for densities of dots less than a fourth threshold density, at least one pixel value corresponding to a pixel that, if unmarked, would separate horizontally or vertically adjacent dots, is “on”, the fourth threshold density being greater than the third threshold density. 
     
     
       9. The process of  claim 8 , wherein M and N are both at least four, and the at least one pixel value corresponds to a pixel at or near to the middle of a row of horizontally adjacent pixels or column of vertically adjacent pixels that, if unmarked, would separate horizontally or vertically adjacent dots. 
     
     
       10. The process of  claim 3 , wherein for pairs of horizontally adjacent dots, at least one pixel value corresponding to a pixel of a column of vertically adjacent pixels that, if unmarked, would separate the dots, is “on”, and for pairs of vertically adjacent dots, at least one pixel value corresponding to a pixel of a row of horizontally adjacent pixels that, if unmarked, would separate the dots, is “on”. 
     
     
       11. The process of  claim 10 , wherein M and N are both at least four, and the at least one “on” pixel value corresponding to the pixel of the column of vertically adjacent pixels is at or near to the middle of the column and the at least one “on” pixel value corresponding to the pixel of the row of horizontally adjacent pixels is at or near to the middle of the row. 
     
     
       12. An output device having non-transitory computer readable storage media including computer-executable instructions that when executed direct the output device to perform the process of  claim 1 . 
     
     
       13. A method for electronically generating 1-bit image data from multiple-bit image data, the 1-bit image data comprising “on” and “off” pixel values, each pixel value of the 1-bit image data corresponding to a pixel of an output medium, which pixel an output device would attempt to mark when printing the 1-bit image data if the pixel value were “on”, the method comprising the steps of:
 storing, by a computer system, multiple-bit image data comprising multiple-bit pixel values in electronic memory; and 
 deriving, by a computer system, from the multiple-bit pixel values and storing in electronic memory 1-bit image data that produces when printed an image constituted by dots, each dot corresponding to a plurality of pixel values of the 1-bit image data, which pixel values correspond to a block of M*N horizontally and/or vertically adjacent pixels of an output medium, at least one of M and N being greater than one, wherein for at least some of the dots, where M or N is equal to one, a pixel value corresponding to a first or last pixel of a row of horizontally adjacent pixels, or to a first or last pixel of a column of vertically adjacent pixels, is “off”, and where both M and N are greater than one, at least one pixel value corresponding to a pixel of a first or last row of horizontally adjacent pixels is “off” and/or at least one pixel value corresponding to a pixel of a first or last column of vertically adjacent pixels is “off”. 
 
     
     
       14. Computer Non-transitory computer readable storage media including computer-executable instructions that when executed direct a computer to perform the method of  claim 13 . 
     
     
       15. A computer programmed to perform the method of  claim 13 . 
     
     
       16. A computer system executed process for generating 1-bit image data from multiple-bit image data, the process comprising the steps of:
 receiving, by the computer system, multiple-bit image data comprising multiple-bit pixel values; and   deriving, by the computer system, from the multiple-bit pixel values 1-bit image data comprising “on” and “off” pixel values, each pixel value of the 1-bit image data corresponding to a pixel of an output medium, which pixel an output device would attempt to mark when printing the 1-bit image data if the pixel value were “on”, the 1-bit image data producing when printed an image constituted by dots, each dot corresponding to a plurality of pixel values of the 1-bit image data, which pixel values correspond to a block of M*N horizontally and/or vertically adjacent pixels of the output medium, at least one of M and N being greater than one,   wherein the process further comprises converting dots to reduced-sized dots within the 1-bit image data where dot density is greater than a first threshold density, wherein converting a dot to a reduced-size dot comprises:   determining that the dot is where the dot density is greater than the first threshold density, and   setting one or more pixel values of the dot, which dot corresponds to an M*N block of horizontally and/or vertically adjacent pixels, to “off” rather than “on” within the 1-bit image data, wherein for at least some of the dots;   where M or N is equal to one, a pixel value corresponding to a first or last pixel of a row of horizontally adjacent pixels, or to a first or last pixel of a column of vertically adjacent pixels of the M*N block, is set to “off” rather than “on”, and   where both M and N are greater than one, at least one pixel value corresponding to a pixel of a first or last row of horizontally adjacent pixels of the M*N block is set to “off” rather than “on” and/or at least one pixel value corresponding to a pixel of a first or last column of vertically adjacent pixels of the M*N block is set to “off” rather than “on”.    
     
     
       17. The process of  claim 16 , wherein the 1-bit image data produce when printed an image constituted by a plurality of densities of dots.  
     
     
       18. The process of  claim 16 , wherein both of M and N of the M*N block are greater than one, at least one pixel value corresponding to a pixel of at least one of first and last rows of horizontally adjacent pixels of the M*N block is set to “off” rather than “on” and at least one pixel value corresponding to a pixel of at least one of first and last columns of vertically adjacent pixels of the M*N block is set to “off” rather than “on”.  
     
     
       19. The process of  claim 18 , wherein the pixel values corresponding to the pixels of at least one of first and last rows of horizontally adjacent pixels of the M*N block and at least one of first and last columns of vertically adjacent pixels of the M*N block are set to “off” rather than “on”.  
     
     
       20. The process of  claim 18 , wherein for pairs of horizontally adjacent dots, at least one pixel value corresponding to a pixel of a column of vertically adjacent pixels that, if unmarked, would separate the dots, is set to “on”, and for pairs of vertically adjacent dots, at least one pixel value corresponding to a pixel of a row of horizontally adjacent pixels that, if unmarked, would separate the dots, is set to “on”.  
     
     
       21. The process of  claim 20 , wherein M and N of the M*N block are both at least four, and the at least one “on” pixel value corresponding to the pixel of the column of vertically adjacent pixels is at or near to the middle of the column and the at least one “on” pixel value corresponding to the pixel of the row of horizontally adjacent pixels is at or near to the middle of the row.  
     
     
       22. The process of  claim 16 , wherein M and N of the M*N block are both greater than one and for densities of dots less than a second threshold density, pixel values of the M*N block corresponding to pixels that, if unmarked, would separate horizontally or vertically adjacent dots, are set to “on”, the second threshold density being greater than the first threshold density.  
     
     
       23. The process of  claim 22 , wherein for densities of dots less than a third threshold density, at least one pixel value corresponding to a pixel that, if unmarked, would separate horizontally or vertically adjacent dots, is set to “off”, the third threshold density being greater than the second threshold density.  
     
     
       24. The process of  claim 23 , wherein for densities of dots less than a fourth threshold density, at least one pixel value corresponding to a pixel that, if unmarked, would separate horizontally or vertically adjacent dots, is set to “on”, the fourth threshold density being greater than the third threshold density.  
     
     
       25. The process of  claim 24 , wherein M and N of the M*N block are both at least four, and the at least one pixel value corresponds to a pixel at or near to the middle of a row of horizontally adjacent pixels or column of vertically adjacent pixels that, if unmarked, would separate horizontally or vertically adjacent dots.  
     
     
       26. An output device having non-transitory computer readable storage media including computer-executable instructions that when executed direct the output device to perform the process of  claim 16 .  
     
     
       27. A method for electronically generating 1-bit image data from multiple-bit image data, the 1-bit image data comprising “on” and “off” pixel values, each pixel value of the 1-bit image data corresponding to a pixel of an output medium, which pixel an output device would attempt to mark when printing the 1-bit image data if the pixel value were “on”, the method comprising the steps of:
 storing, by a computer system, multiple-bit image data comprising multiple-bit pixel values in electronic memory; and 
 deriving, by a computer system, from the multiple-bit pixel values and storing in electronic memory 1-bit image data that produces when printed an image constituted by dots, each dot corresponding to a plurality of pixel values of the 1-bit image data, which pixel values correspond to a block of M*N horizontally and/or vertically adjacent pixels of the output medium, at least one of M and N being greater than one, 
 wherein the deriving further comprises, converting dots to reduced-sized dots where dot density is greater than a first threshold density, wherein converting a dot to a reduced-size dot comprises: 
 determining that the dot is where the dot density is greater than the first threshold density, and 
 setting one or more pixel values of the dot, which dot corresponds to an M*N block of horizontally and/or vertically adjacent pixels to “off” rather than “on” within the 1-bit image data, wherein for at least some of the dots; 
 where M or N is equal to one, a pixel value corresponding to a first or last pixel of a row of horizontally adjacent pixels, or to a first or last pixel of a column of vertically adjacent pixels of the M*N block, is set to “off” rather than “on”, and 
 where both M and N are greater than one, at least one pixel value corresponding to a pixel of a first or last row of horizontally adjacent pixels of the M*N block is set to “off” rather than “on” and/or at least one pixel value corresponding to a pixel of a first or last column of vertically adjacent pixels of the M*N block is set to “off” rather than “on”.  
 
     
     
       28. Non-transitory computer readable storage media including computer-executable instructions that when executed direct a computer to perform the method of  claim 27 .  
     
     
       29. A computer programmed to perform the method of  claim 27 .  
     
     
       30. A computer system executed process for generating 1-bit image data from multiple-bit image data, the process comprising the steps of:
 receiving, by the computer system, multiple-bit image data comprising multiple-bit pixel values; and   deriving, by the computer system, from the multiple-bit pixel values 1-bit image data comprising “on” and “off” pixel values, each pixel value of the 1-bit image data corresponding to a pixel of an output medium, which pixel an output device would attempt to mark when printing the 1-bit image data if the pixel value were “on”, the 1-bit image data producing when printed an image constituted by dots, each corresponding to a plurality of pixel values of the 1-bit image data, which pixel values correspond to a respective block of M*N horizontally and/or vertically adjacent pixels of the output medium, at least one of M and N being greater than one,   the deriving further comprising converting dots to reduced-sized dots within the 1-bit image data, wherein converting a dot to a reduced-sized dot comprises:   configuring pixel values of the dot, which dot corresponds to an M*N block of horizontally and/or vertically adjacent pixels, such that at least one of the pixel values is “off” rather than “on”, the pixel values further configured such that, for at least some of the dots:   where M or N is equal to one, a pixel value corresponding to a first or last pixel of a row of horizontally adjacent pixels, or to a first or last pixel of a column of vertically adjacent pixels, is “off” rather than “on” within the 1-bit image data, and   where both M and N are greater than one, pixel values corresponding to at least one of a first and last row of horizontally adjacent pixels are “off” rather than “on” and pixel values corresponding to at least one of a first and last column of vertically adjacent pixels are “off” rather than “on” within the 1-bit image data.    
     
     
       31. The process of  claim 30 , wherein the 1-bit image data produce when printed an image constituted by a plurality of densities of dots.  
     
     
       32. The process of  claim 31 , wherein the deriving further comprises converting each dot of the image to a respective reduced-sized dot within the 1-bit image data, including dots within portions of the image of which densities of dots are low.  
     
     
       33. The process of  claim 30 , wherein the deriving further comprises:
 applying a screening algorithm to the multiple-bit image data to produce an intermediate array, wherein “on” values of the intermediate array correspond to dots of the image; and   converting each “on” value of the intermediate array to a respective reduced-sized dot within the image data.    
     
     
       34. The process of  claim 30 , wherein the deriving further comprises:
 converting “on” values of an intermediate array to full-sized dots within the 1-bit image data where dot density is less than a first density threshold, each pixel value corresponding to the full-sized dots comprising an “on” pixel value; and   converting “on” values of the intermediate array to reduced-sized dots within the 1-bit image data where the dot density is greater than the first density threshold.    
     
     
       35. The process of  claim 34 , wherein M and N of the M*N block are both greater than one and for densities of dots less than a second threshold density, pixel values of the M*N block corresponding to pixels that, if unmarked, would separate horizontally or vertically adjacent dots, are set to “on”, the second threshold density being greater than the first threshold density.  
     
     
       36. The process of  claim 35 , wherein for densities of dots less than a third threshold density, at least one pixel value corresponding to a pixel that, if unmarked, would separate horizontally or vertically adjacent dots, is “off”, the third threshold density being greater than the second threshold density.  
     
     
       37. The process of  claim 36 , wherein for densities of dots less than a fourth threshold density, at least one pixel value corresponding to a pixel that, if unmarked, would separate horizontally or vertically adjacent dots, is “on”, the fourth threshold density being greater than the third threshold density.  
     
     
       38. The process of  claim 37 , wherein M and N of the M*N block are both at least four, and the at least one pixel value corresponds to a pixel at or near to the middle of a row of horizontally adjacent pixels or column of vertically adjacent pixels that, if unmarked, would separate horizontally or vertically adjacent dots.  
     
     
       39. The process of  claim 30 , wherein for pairs of horizontally adjacent dots, at least one pixel value corresponding to a pixel of a column of vertically adjacent pixels that, if unmarked, would separate the dots, is “on”, and for pairs of vertically adjacent dots, at least one pixel value corresponding to a pixel of a row of horizontally adjacent pixels that, if unmarked, would separate the dots, is “on”.  
     
     
       40. The process of  claim 39 , wherein M and N of the M*N block are both at least four, and the at least one “on” pixel value corresponding to the pixel of the column of vertically adjacent pixels is at or near to the middle of the column and the at least one “on” pixel value corresponding to the pixel of the row of horizontally adjacent pixels is at or near to the middle of the row.  
     
     
       41. An output device having non-transitory computer readable storage media including computer-executable instructions that when executed direct the output device to perform the process of  claim 30 .  
     
     
       42. A method for electronically generating 1-bit image data from multiple-bit image data, the 1-bit image data comprising “on” and “off” pixel values, each pixel value of the 1-bit image data corresponding to a pixel of an output medium, which pixel an output device would attempt to mark when printing the 1-bit image data if the pixel value were “on”, the method comprising the steps of:
 storing, by a computer system, multiple-bit image data comprising multiple-bit pixel values in electronic memory; and 
 deriving, by a computer system, from the multiple-bit pixel values and storing in electronic memory 1-bit image data that produces when printed an image constituted by dots, each corresponding to a plurality of pixel values of the 1-bit image data, which pixel values correspond to a block of M*N horizontally and/or vertically adjacent pixels of the output medium, at least one of M and N being greater than one, 
 the deriving further comprising converting the dots to reduced-sized dots within the 1-bit image data, wherein converting a dot to a reduced-size dot comprises: 
 configuring pixel values of the dot, which dot corresponds to an M*N block of horizontally and/or vertically adjacent pixels such that at least one of the pixel values is “off” rather than “on”, the pixel values further configured such that, for at least some of the dots; 
 where M or N is equal to one, a pixel value corresponding to a first or last pixel of a row of horizontally adjacent pixels, or to a first or last pixel of a column of vertically adjacent pixels, is “off” rather than “on” within the 1-bit image data, and 
 where both M and N are greater than one, pixel values corresponding to at least one of a first and last row of horizontally adjacent pixels are “off” rather than “on” and pixel values corresponding to at least one of a first and last column of vertically adjacent pixels are “off” rather than “on” within the 1-bit image data.  
 
     
     
       43. The method of  claim 42 , wherein the deriving further comprises:
 converting dots to reduced-sized dots where dot density is greater than a first threshold density; and   converting dots to full-sized dots where dot density is less than the first threshold density, the full-sized dots corresponding to respective M*N blocks of “on” pixel values.    
     
     
       44. Non-transitory computer readable storage media including computer-executable instructions that when executed direct a computer to perform the method of claim 42.  
     
     
       45. A computer programmed to perform the method of  claim 42 .  
     
     
       46. A computer system executed process for generating 1-bit image data from multiple-bit image data, the process comprising the steps of:
 receiving, by the computer system, multiple-bit image data comprising multiple-bit pixel values; and   deriving, by the computer system, from the multiple-bit pixel values, 1-bit image data comprising “on” and “off” pixel values, each pixel value of the 1-bit image data corresponding to a pixel of an output medium, which pixel an output device would attempt to mark when printing the 1-bit image data if the pixel value were “on”, the 1-bit image data producing when printed an image constituted by dots, each dot corresponding to a plurality of pixel values of the 1-bit image data, which pixel values correspond to a respective block of M*N horizontally and/or vertically adjacent pixels of the output medium, at least one of M and N being greater than one,   wherein the deriving further comprises:
 using full-sized dots where dot density is less than a first threshold density, and 
 using reduced-sized dots where the dot density is greater than the first threshold density, the reduced-sized dots corresponding to pixel values of the 1-bit image data, which pixel values correspond to respective M*N blocks of pixels, the pixel values configured such that, for at least some of the dots:
 where M or N is equal to one, a pixel value corresponding to a first or last pixel of a row of horizontally adjacent pixels, or to a first or last pixel of a column of vertically adjacent pixels of the corresponding M*N block of pixels is “off” rather than “on”, and 
 where both M and N are greater than one, at least one pixel value corresponding to a pixel of a first or last row of horizontally adjacent pixels of the corresponding M*N block of pixels is “off” rather than “on” and/or at least one pixel value corresponding to a pixel of a first or last column of vertically adjacent pixels of the corresponding M*N block of pixels is “off” rather than “on”.  
 
   
     
     
       47. The process of  claim 46 , wherein the 1-bit image data produce when printed an image constituted by a plurality of densities of dots.  
     
     
       48. The process of  claim 46 , wherein where both of M and N are greater than one, the pixel values are further configured such that at least one pixel value corresponding to a pixel of at least one of first and last rows of horizontally adjacent pixels of the M*N block of pixels is “off” rather than “on” and at least one pixel value corresponding to a pixel of at least one of first and last columns of vertically adjacent pixels of the M*N block of pixels is “off” rather than “on”.  
     
     
       49. The process of  claim 48 , wherein the process further comprises deriving the 1-bit image data such that:
 for pairs of horizontally adjacent dots, at least one pixel value corresponding to a pixel of a column of vertically adjacent pixels that, if unmarked, would separate the dots, is “on” rather than “off”, and   for pairs of vertically adjacent dots, at least one pixel value corresponding to a pixel of a row of horizontally adjacent pixels that, if unmarked, would separate the dots, is “on” rather than “off”.    
     
     
       50. The process of  claim 49 , wherein M and N are both at least four, and the at least one “on” pixel value corresponding to the pixel of the column of vertically adjacent pixels is at or near to a middle of the column and the at least one “on” pixel value corresponding to the pixel of the row of horizontally adjacent pixels is at or near to a middle of the row.  
     
     
       51. The process of  claim 46 , wherein the pixel values are further configured such that the pixel values corresponding to the pixels of at least one of the first and last rows of horizontally adjacent pixels of the M*N block of pixels and at least one of the first and last columns of vertically adjacent pixels of the M*N block of pixels are “off” rather than “on”.  
     
     
       52. The process of  claim 46 , wherein M and N are both greater than one and for densities of dots less than a second threshold density, pixel values corresponding to pixels that, if unmarked, would separate horizontally or vertically adjacent dots, are “on” rather than “off”, the second threshold density being greater than the first threshold density.  
     
     
       53. The process of  claim 52 , wherein for densities of dots less than a third threshold density, at least one pixel value corresponding to a pixel that, if unmarked, would separate horizontally or vertically adjacent dots, is “off” rather than “on”, the third threshold density being greater than the second threshold density.  
     
     
       54. The process of  claim 53 , wherein for densities of dots less than a fourth threshold density, at least one pixel value corresponding to a pixel that, if unmarked, would separate horizontally or vertically adjacent dots, is “on” rather than “off”, the fourth threshold density being greater than the third threshold density.  
     
     
       55. The process of  claim 54 , wherein M and N are both at least four, and the at least one pixel value corresponds to a pixel at or near to a middle of a row of horizontally adjacent pixels or column of vertically adjacent pixels of the M*N block of pixels that, if unmarked, would separate horizontally or vertically adjacent dots.  
     
     
       56. An output device having non-transitory computer readable storage media including computer-executable instructions that when executed direct the output device to perform the process of  claim 46 .  
     
     
       57. A method for electronically generating 1-bit image data from multiple-bit image data, the 1-bit image data comprising “on” and “off” pixel values, each pixel value of the 1-bit image data corresponding to a pixel of an output medium, which pixel an output device would attempt to mark when printing the 1-bit image data if the pixel value were “on”, the method comprising the steps of:
 storing, by a computer system, multiple-bit image data comprising multiple-bit pixel in electronic memory; and 
 deriving, by a computer system, from the multiple-bit pixel values and storing in electronic memory 1-bit image data that produces when printed an image constituted by dots, each dot corresponding to a plurality of pixel values of the 1-bit image data, which pixel values correspond to a respective block of M*N horizontally and/or vertically adjacent pixels of the output medium, at least one of M and N being greater than one, 
 wherein the deriving further comprises: 
 converting the multiple-bit image data to M*N blocks of pixels of the 1-bit image data, wherein an M*N block comprises one of: 
 a full-sized dot where a dot density is less than a first threshold density, and 
 a reduced-size dot where the dot density is greater than the first threshold density, comprising configuring the M*N block such that, for at least some of the dots: 
 where M or N is equal to one, a pixel value corresponding to a first or last pixel of a row of horizontally adjacent pixels of the M*N block, or to a first or last pixel of a column of vertically adjacent pixels of the corresponding M*N block of pixels, is “off” rather than “on”, and 
 where both M and N are greater than one, at least one pixel value corresponding to a pixel of a first or last row of horizontally adjacent pixels of the corresponding M*N block of pixels is “off” rather than “on” and/or at least one pixel value corresponding to a pixel of a first or last column of vertically adjacent pixels of the corresponding M*N block of pixels is “off” rather than “on”.  
 
     
     
       58. Non-transitory computer readable storage media including computer-executable instructions that when executed direct a computer to perform the method of  claim 57 .  
     
     
       59. A computer programmed to perform the method of  claim 57 .