Dilation of images without resolution conversion to compensate for printer characteristics

• US 5,483,351 A
• Filed: 05/08/1995
• Issued: 01/09/1996
• Est. Priority Date: 09/25/1992
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Mailloux, Louis D., Robson, Thomas
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): FRAHM, ERIC S
• Application Number:
  US08/435,045
• Time in Patent Office: 246 Days
• Field of Search: 358/298, 358/443, 358/447, 358/448, 358/455-466, 347/129, 347/224, 382/54, 382/55, 395/109
• US Class Current: 358/3.27
• CPC Class Codes: G06K 15/128 generating or processing printable items, e.g. characters
• CPC Class Codes: G06T 3/403 Edge-driven scaling; Edge-based scaling
• CPC Class Codes: H04N 1/4092 Edge or detail enhancement

Abstract

An image compensation system which provides dilation or erosion of image features using halfbitting or fullbitting in the rendition of bitmap images, especially on a write-white printer. A region of pixels of an image is isolated which includes two or more correctable pixel locations. A set of state determination rules, based on the formation of pixels in the isolated region, is used to determine a corrected binary pixel state for each of the correctable pixels. Corrections for one correctable pixel may be considered in the state determination rules for adjacent correctable pixels. A single enhanced output pixel is provided for each image input pixel, thereby preserving the original image resolution. Performing enhancements on multiple input pixels simultaneously increases the system throughput.

Claims

1. A method for expanding features of an image represented by a plurality of binary pixels at a state transition portion of the image without affecting resolution of the image, a state transition defined by pixels at a first state adjacent to pixels at a second state, the method comprising the steps of:

storing a group of pixels representing a portion of the image which overlies said state transition in a first storage;

isolating a window in said group of pixels, said window including a pixel formation comprising first and second correctable pixels and pixels surrounding said first and second correctable pixels, said first and second correctable pixels being adjacent to said state transition;

for said first correctable pixel, determining a corrected binary pixel state according to a first set of state determination rules, said first set of state determination rules being based on binary states of said pixels in said pixel formation; and

for said second correctable pixel, determining a corrected binary pixel state according to a second set of state determination rules, said second set of state determination rules being based on binary states of said pixels in said pixel formation and on said corrected binary pixel state of said first correctable pixel.

2. The method of claim 1, wherein the step of isolating said window of pixels further comprises isolating a 4-pixel by 4-pixel region of pixels including four central pixels and pixels surrounding said central pixels, said first and second correctable pixels each being one of said four central pixels.

3. The method of claim 2, wherein the steps of storing a group of pixels, isolating a window of pixels including four central pixels, and determining for first and second correctable pixels a corrected binary pixel state according to state determination rules are repeated so that each pixel in the image is one of said four central pixels.

4. The method of claim 1, wherein said first set of state determination rules further tends to favor a first state over a second state, and said second set of state determination rules further tends to favor a second state over a first state.

5. The method of claim 1, wherein said first state is black, said first set of state determination rules further tending to favor a corrected binary pixel state of black.

6. The method of claim 1, wherein said first state is white, said first set of state determination rules further tending to favor a corrected binary pixel state of white.

7. An apparatus for converting an image represented by a plurality of binary pixels from a first format at a first resolution to a second format at the first resolution, comprising:

means for inputting a portion of said plurality of binary pixels representing the image;

means for isolating a window of pixels in said portion of said plurality of binary pixels representing the image including a pixel formation comprising a plurality of adjacent correctable pixels and pixels surrounding said correctable pixels;

means for storing a set of state determination rules based on said pixel formation;

lookup means for determining a corrected binary pixel state for each correctable pixel according to said set of state determination rules; and

means for outputting said corrected binary pixel states.

8. The apparatus of claim 7, wherein said storing means further comprises means for storing a first set of state determination rules tending to favor a first state over a second state for a first correctable pixel position at portions of the image having a state transition, and means for storing a second set of state determination rules tending to favor a second state over a first state for a second correctable pixel position, said second pixel position being adjacent to said first correctable pixel.

9. A method for converting an image from a first format into a second corrected format in a system for reproducing images image represented by a plurality of pixels, the method comprising the steps of:

storing a group of pixels representing a portion of said image in the first format in a first storage, each of said pixels having a binary state;

isolating a window in said group of pixels including a pixel formation comprising first and second adjacent correctable pixels and pixels surrounding said first and second correctable pixels;

for said first correctable pixel, determining a corrected binary pixel state in said second corrected format according to a set of state determination rules, said state determination rules being based on binary states of said pixels in said pixel formation; and

for said second correctable pixel, determining a corrected binary pixel state in said second corrected format according to said set of state determination rules, said state determination rules for said second correctable pixel position further being based on said corrected binary pixel state of said first correctable pixel.

10. The method of claim 9, wherein for said first correctable pixel, said state determination rules further tending to favor a first state over a second state at portions of the image having a state transition;

and

for said second correctable pixel, said state determination rules further tending to favor a second state over a first state at portions of the image having a state transition.

11. The method of claim 9, wherein the steps of storing a group of pixels, isolating a window of pixels including first and second correctable pixels, and determining for said first and second pixels a corrected binary pixel state according to state determination rules are repeated so that each pixel in the image is one of said first or second pixels.

12. The method of claim 9, wherein for half bit dilation said isolating step further includes isolating a window of the pixels in said pixel group including a pixel formation comprising a 4-pixel by 4-pixel region including four central pixel positions E1, E2, E3, and E4, said first and second correctable pixels each being located at one of said four central pixel positions, said state determination rules being as follows:

for central pixel position E1, said pixel being surrounded by pixels (a,b,c,d,f,g,h,i,j,k,l,m,n,o,p) which are adjacent and surrounding said correctable pixel E1 in said pixel formation;

if pixels (b,d) are at a first state;

or

if pixels (d,h) are at a first state and pixel (f) is at a second state;

or

if pixels (a,b) are at a first state;

or

if pixels (a,d) are at a first state;

or

if pixels (b,c) are at a first state and pixel (h) is at a second state;

or

if pixels (d,g) are at a first state and pixel (f) is at a second state;

or

if pixel (b) is at a first state and pixels (a,c,d,f,g,h,i,j,m) are at a second state;

or

if pixel (d) is at a first state and pixels (a,b,c,f,g,h,i,l,o) are at a second state;

make output pixel (E1)=said first state;

otherwise E1=E1;

for central pixel position E2, said pixel being surrounded by pixels (a,b,c,d,f,g,h,i,j,k,l,m,n,o,p) which are adjacent and surrounding said correctable pixel E2 in said pixel formation;

if pixels (b,d) are at a first state;

or

if pixels (d,h) are at a first state and pixel (f) is at a second state;

or

if pixel (b) is at a first state and pixels (a,c,d,f,g,h,i,j,p) are at a second state;

or

if pixel (d) is at a first state and pixels (a, b,c,f,g,h,i,l) are at a second state;

make output pixel (E2)=said first state;

otherwise E2=E2;

for central pixel position E3, said pixel being surrounded by pixels (a,b,c,d,f,g,h,i,j,k,l,m,n,o,p) which are adjacent and surrounding said correctable pixel E3 in said pixel formation;

if pixels (b,d) are at a first state;

or

if pixels (d,h) are at a first state and pixel (f) is at a second state;

or

if pixels (a,b) are at a first state;

or

if pixels (a,d) are at a first state;

or

if pixels (b,c) are at a first state and pixel (h) is at a second state;

or

if pixels (d,g) are at a first state and pixel (f) is at a second state;

or

if pixel (b) is at a first state and pixels (a,c,d,f,g,h,i,j) are at a second state;

or

if pixel (d) at a first state and pixels (a,b,c,f,g,h,i,p) are at a second state;

make output pixel (E3)=said first state;

otherwise E3=E3; and

for central pixel position E4, said pixel being surrounded by pixels (a,b,c,d,f,g,h,i,j,k,l,m,n,o,p) which are adjacent and surrounding said correctable pixel E4 in said pixel formation;

if pixels (b,d) are at a first state;

or

if pixels (d,h) are at a first state and pixel (f) is at a second state;

or

if pixel (b) is at a first state and pixels (a,c,d,f,g,h,i,j) are at a second state;

or

if pixel (d) is at a first state and pixels (a,b,c,f,g,h,i,j,o) are at a second state;

make output pixel (E4)=said first state;

otherwise E4=E4.

13. The method of claim 9, wherein for full bit dilation said isolating step further includes isolating a window of the pixels of said image portion including a pixel formation comprising a 4-pixel by 4-pixel area including four central pixel positions, said first and second correctable pixels each being located at one of said four central pixel positions, said state determination rules being as follows:

for each central pixel position E, said pixel being surrounded by pixels (a,b,c,d,f,g,h,i,j,k,l,m,n,o,p) which are adjacent and surrounding said correctable pixel E in said pixel formation;

if pixels (a,b) are at said first state;

or

if pixels (a,d) are at said first state and pixel (f) is at said second state;

or

if pixels (b,d) are at said first state;

or

if pixels (d,h) are at said first state and pixel (f) is at said second state;

or

if pixels (b,c) are at said first state and pixel (h) is at said second state;

or

if pixels (d,g) are at said first state and pixel (f) is at said second state;

or

if pixel (b) is at said first state and pixels (a,c,d,f,g,h,i) are at said second state;

or

if pixel (a) is at said first state and pixels (b,c,d,f,g,h,i) are at said second state;

make the state of output pixel (E)=said first state;

otherwise (E)=(E).