Grayscale character generator and method

Claim 3

The method set forth in claim 1, wherein said set of rectangles representing the rectangular decomposition of each said bi-level master character excludes rectangles less than a certain specified size.

Claim 4

The method set forth in claim 1, wherein said first providing step provides a set of nonoverlapping rectangles for each said master character.

Claim 5

The method set forth in claim 1, wherein said second providing step provides a plurality of filter arrays, and said generating step includes the step of specifying one of said plurality of filter arrays to be used with each of said multiplicity of rectangles; whereby different filter arrays can be used with different rectangles when generating grayscale characters.

Claim 8

The method set forth in claim 5, wherein each said filter array is a two dimensional array of elements, including four corner elements; said third providing step provides four different summed area filter arrays for at least one said fitler array, the elements in each said summed area filter array representing the sum of corresponding rectangular subsets of said filter array when a corresponding one of said four corner elements is included in said rectangular subset; and said adding step includes, when said determined intersection includes at least one of said four corner elements of said specified filter array, the steps of selecting the corresponding one of said four different summed area filter arrays, selecting from said selected summed area filter array a single element which corresponds to the rectangular subset of said filter array in said determined intersection, and adding the value of said selected single element to the value of said grayscale pixel.

Claim 11

The method set forth in claim 7, wherein said generating step includes the step of assigning to each said grayscale pixel a predefined value corresponding to a black pixel if the filter support for said specified filter array is totally inside said rectangle when said filter array is centered at the said grayscale pixel in said sampling grid.

Claim 12

The method set forth in claim 8, wherein each said filter array is a two dimensional array of elements including four corner elements, and said third providing step provides a set of four different summed area filter arrays for at least one said filter array, the elements in each said summed area filter array representing the sum of corresponding rectangular subsets of said filter array when a corresponding one of said four corner elements is included in said rectangular subset; and said adding step includes selecting a summed area filter array from said set of four different summed area filter arrays, in accordance with the ones of said four corner elements in said determined intersection.

Claim 13

The method set forth in claim 7, wherein said second providing step provides a plurality of filter arrays, and said generating step includes the step of specifying one of said plurality of filter arrays to be used with each of said multiplicity of rectangles; whereby different filter arrays can be used with different rectangles when generating grayscale characters.

Claim 14

Apparatus for generating grayscale characters from bi-level master characters, comprising: first storage means for storing master font data representing a multiplicity of high resolution bi-level master characters, each said bi-level master character comprising a high resolution grid of bi-level pixel values; said master font data including a set of rectangles representing the rectangular decomposition of each bi-level master character to be used; second storage means for storing filter data, including at least one filter array for converting master characters into grayscale characters, each filter array having a designated center and an array of elements with a resolution corresponding to the resolution of said master characters, the values of said filter elements representing the contributions of corresponding bi-level master pixel values to a grayscale pixel located at the center of said filter; each said filter array having a filter support corresponding to the extent of said filter array's nonzero elements; said filter array being stored in the form of a summed area filter array, wherein each element in said summed area filter array represents the sum of the filter array elements in a corresponding rectangular subarray of said filter array; and data processing means for generating a specified grayscale character, including software means for processing at least a multiplicity of said rectangles in said set of rectangles representing the decomposition of a corresponding one of said master characters, said software means including: means for specifying a filter array to be used with said rectangle; means for specifying a sampling grid of grayscale pixels having a lower resolution than the resolution of said selected bi-level master character; means for specifying the location of said rectangle with respect to said sampling grid of grayscale pixels; means for determining the grayscale pixels in said sampling grid affected by said rectangle by determining the grayscale pixels for which said filter support of said specified filter array overlaps said rectangle when said specified filter array is centered on said grayscale pixels; and grayscale value assigning means for assigning values to each said grayscale pixel affected by said rectangle, including: intersection determining means for determining the intersection of said rectangle and said specified filter array, centered at said grayscale pixel; and adding means for adding to the value of said grayscale pixel the value of an element in said summed area filter array corresponding to said specified filter array, said element corresponding to the subset of said filter array in said determined intersection.

Claim 15

Apparatus for generating grayscale characters from bi-level master characters, comprising: first storage means for storing master font data representing a multiplicity of high resolution bi-level master characters, each said bi-level master character comprising a high resolution grid of bi-level pixel values; said master font data including a set of rectangles representing the rectangular decomposition of each bi-level master character to be used; second storage means for storing filter data, including at least one filter array for converting master characters into grayscale characters, each filter array having a designated center and an array of elements with a resolution corresponding to the resolution of said master characters, the values of said filter elements representing the contributions of corresponding bi-level master pixel values to a grayscale pixel located at the center of said filter; each said filter array having a filter support corresponding to the extent of said filter array's nonzero elements; said filter array being stored in the form of a summed area filter array, wherein each element in said summed area filter array represents the sum of the filter array elements in a corresponding rectangular subarray of said filter array; and data processing means for generating a specified grayscale character, including software means for processing at least a multiplicity of said rectangles in said set of rectangles representing the decomposition of a corresponding one of said master characters, said software means including: means for specifying a filter array to be used with said rectangle; means for specifying a sampling grid of grayscale pixels having a lower resolution than the resolution of said selected bi-level master character; means for specifying the location of said rectangle with respect to said sampling grid of grayscale pixels; means for determining the grayscale pixels in said sampling grid affected by said rectangle by determining the grayscale pixels for which said filter support of said specified filter array overlaps said rectangle when said specified filter array is centered on said grayscale pixels; and grayscale value assigning means for assigning values to each said grayscale pixel affected by said rectangle, including: intersection determining means for determining the intersection of said rectangle and said specified filter array, centered at said grayscale pixel; and adding means for adding to the value of said grayscale pixel the value of an element in said summed area filter array corresponding to said specified filter array, said element corresponding to the subset of said filter array in said determined intersection.

Claim 16

The apparatus set forth in claim 11, wherein said grayscale value assigning means further includes black pixel assigning means for assigning to a grayscale pixel a predefined value corresponding to a black pixel if the filter support for said specified filter array would be totally inside said rectangle when said filter array is centered at said grayscale pixel in said sampling grid.

Claim 17

The apparatus set forth in claim 11, wherein said second storage means stores a plurality of filter arrays, and said data processing means includes means for specifying one of said plurality of filter arrays to be used with each of said multiplicity of rectangles; whereby different filter arrays can be used with different rectangles when generating grayscale characters.

Claim 18

The apparatus set forth in claim 11, wherein each said filter array is a two dimemsional array of elements including four corner elements, and said second storage means stores a set of four different summed area filter arrays for at least one said filter array, the elements in each said summed area filter array representing the sum of corresponding rectangular subsets of said filter array when a corresponding one of said four corner elements is included in said rectangular subset; and said adding means includes means for selecting a summed area filter array from said set of four different summed area filter arrays, in accordance with the ones of said four corner elements in said determined intersection.