Surround Error Diffusion

• US 20100246987A1
• Filed: 03/27/2009
• Published: 09/30/2010
• Est. Priority Date: 03/27/2009
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Chang, Ching-Wei
• Granted Patent: US 8,320,694 B2
• Time in Patent Office: Days
• US Class Current: 382/252
• CPC Class Codes: H04N 1/4052 by error diffusion, i.e. transferring the binarising error to neighbouring dot decisions

Abstract

Machine-enabled methods of, and system, and processor readable media, embodiments for, tone quantization error diffusion.

Claims

1. A method of tone error diffusion in a pixel array comprising:

receiving a pixel array comprising a second line of pixels interposed between a first line of pixels and a third line of pixels;

a first stage process comprising;

determining a tone error for a first pixel of the first line of pixels of the pixel array based on an input value of the first pixel of the first line of pixels and at least one threshold value, the first pixel having only one lineally adjacent pixel;

determining a tone error for a second pixel lineally adjacent to the first pixel of the first line of pixels based on;

an input value of the second pixel of the first line of pixels, a portion of the tone error of the first pixel of the first line of pixels, and the at least one threshold value;

determining a tone error for a first pixel of the third line of pixels of the pixel array based on an input value of the first pixel of the third line of pixels and at least one threshold value, the first pixel of the third line of pixels having only one lineally adjacent pixel; and

determining a tone error for a second pixel lineally adjacent to the first pixel of the third line of pixels based on;

an input value of the second pixel of the third line of pixels, a portion of the tone error of the first pixel of the third line of pixels, and the at least one threshold value; and

a second stage process comprising;

determining a tone error for a first pixel of the second line of pixels of the pixel array based on;

an input value for the first pixel of the third line of pixels, a portion of the tone error of each adjacent pixel of the first line of pixels, a portion of the tone error of each adjacent pixel of the third line of pixels, and the at least one threshold value, the first pixel of the second line of pixels having only one lineally adjacent pixel; and

determining a tone error for a second pixel lineally adjacent to the first pixel of the second line of pixels based on;

an input value for the second pixel of the third line of pixels, a portion of the tone error of the first pixel of the second line of pixels, a portion of the tone error of each adjacent pixel of the first line of pixels and a portion of the tone error of each adjacent pixel of the third line of pixels, and at least one threshold value.

2. The method of tone error diffusion of claim 1 wherein the first stage process further comprises:

iteratively determining a tone error for each successive pixel lineally adjacent to the second pixel of the first line of pixels based on an input value of the successive pixel of the first line of pixels, a portion of the determined tone error of the lineally adjacent pixel of the first line of pixels, and the at least one threshold value;

iteratively determining a tone error for each successive pixel lineally adjacent to the second pixel of the third line of pixels based on an input value of the successive pixel of the third line of pixels, a portion of the determined tone error of the lineally adjacent pixel of the third line of pixels, and the at least one threshold value; and

wherein the second stage process further comprises;

iteratively determining a tone error for each successive pixel lineally adjacent to the second pixel of the second line of pixels based on;

an input value of the successive pixel of the second line of pixels, a portion of the determined tone error of the lineally adjacent pixel of the second line of pixels, a portion of the tone error of each adjacent pixel of the first line of pixels and a portion of the tone error of each adjacent pixel of the third line of pixels, and at least one threshold value.

3. The method of tone error diffusion of claim 1 wherein the step of determining a tone error for the second pixel lineally adjacent to the first pixel of the second line of pixels of the second stage process is based on:

an input value for the second pixel of the second line of pixels, a portion of the tone error of the first pixel of the second line of pixels, a portion of the tone error of each pixel of the first line of pixels within two pixel spaces from a pixel of the first line immediately adjacent to the second pixel of the second line, and a portion of the tone error of each pixel of the third line of pixels within two pixel spaces from a pixel of the third line immediately adjacent to the second pixel of the second line, and at least one threshold value.

4. A method of diffusing tone quantization error of a digital image comprising:

receiving a digital image having input pixel tone levels according to i rows and j columns;

for alternate rows of pixels of the digital image;

quantizing an assigned pixel tone level of each pixel, or S_i,j, in series j, wherein the assigned tone level, or S_i,j, comprises an input tone value, or P_i,j, and, a partial tone quantization error, or N<sub>i,j−

1</sub>, from the last quantized pixel in row i, if present; and

determining a total quantization error, or D_i,j comprising a partial tone quantization error, or N_i,j, and a remainder tone quantization error, or E_i,j, and

storing the remainder tone quantization error, or E_i,j; and

for rows of pixels interposed between the alternate rows of pixels of the digital image;

quantizing an assigned pixel tone level of each pixel, or S_i,j, in series j, of row i, wherein the assigned tone level, or S_i,j, comprises;

(a) an input tone value, or P_i,j;

(b) a partial tone quantization error, or N<sub>i,j−

1</sub>, from the last quantized pixel in row i, if present; and

(c) a sum of a weighted remainder tone quantization errors of two or more of the nearest neighbor pixels of the alternate rows comprising the sum;

w₂*E<sub>i−

1,j</sub>+w₅*E_i+1,j+w₆*E<sub>i+1,j−

1</sub>) and, at least one of;

(i) the sum;

w₁*E<sub>i−

1,j−

1</sub>+w₄*E<sub>i+1,j−

1</sub> and (ii) the sum;

w₃*E<sub>i−

1,j+1</sub>+w₆*E_i+1,j+1; and

determining a total quantization error, or D_i,j comprising a partial tone quantization error, N_i,j.

5. The method of diffusing tone quantization error of a digital image of claim 4 wherein the steps of quantizing the assigned pixel tone level of each pixel, or S_i,j, in series j is based on a threshold value.

6. The method of diffusing tone quantization error of a digital image of claim 4 wherein for rows of pixels interposed between the alternate rows of pixels of the digital image, the quantizing step comprises:

quantizing an assigned pixel tone level of each pixel, or S_i,j, in series j, of row i, wherein the assigned tone level, or S_i,j, comprises;

(a) an input tone value, or P_i,j;

(b) a partial tone quantization error, or N<sub>i,j−

1</sub>, from the last quantized pixel in row i, if present; and

(c) if remainder tone quantization errors E<sub>i−

1,j−

1</sub>, E<sub>i+1,j−

1</sub>, E<sub>i−

1,j+1</sub>, and E_i+1,j+1 are present, a sum of weighted remainder tone quantization errors of the nearest neighbor pixels of the alternate rows comprising;

the sum;

w₁*E<sub>i−

1,j−

1</sub>+w₂*E<sub>i−

1,j</sub>+w₃*E<sub>i−

1,j+1</sub>+w₄*E<sub>i+1,j−

1</sub>+w₅*E_i+1,j+w₆*E_i+1,j+1.

7. The method of diffusing tone quantization error of a digital image of claim 6 wherein w₁=⅛

;

w₂= 2/8;

w₃=⅛

;

w₄=⅛

;

w₅= 2/8; and

w₆=⅛

.

8. A system for producing image output comprising:

a image tone quantization module configured to;

input a digital image having input pixel tone levels according to i rows and j columns; and

for alternate rows of pixels of the input digital image;

quantize an assigned pixel tone level of each pixel, or S_i,j, in series j, of row i, wherein the assigned tone level, or S_i,j, comprises an input tone value, or P_i,j, and, if present, a partial tone quantization error, or N<sub>i,j−

1</sub>, from a last quantized pixel; and

determine a total quantization error, or D_i,j comprising a partial tone quantization error, or N_i,j and remainder tone quantization error, or E_i,j, and

store the remainder tone quantization error, or E_i,j; and

for rows of pixels interposed between the alternate rows of pixels of the input digital image;

quantize an assigned pixel tone level of each pixel, or S_i,j, in series j, of row i wherein the assigned tone level, or S_i,j, comprises;

(a) an input tone value, or P_i,j;

(b) a partial tone quantization error, or N<sub>i,j−

1</sub>, from the last quantized pixel in row i, if present; and

(c) a sum of a weighted remainder tone quantization errors of two or more of the nearest neighbor pixels of the alternate rows comprising the sum;

w₂*E<sub>i−

1,j−

1</sub>+w₅*E_i+1,j+w₆*E<sub>i+1,j−

1</sub>) and, at least one of;

(i) the sum;

w₁*E<sub>i−

1,j−

1</sub>+w₄*E<sub>i+1,j−

1</sub> and (ii) the sum;

w₃*E<sub>i−

1,j+1</sub>+w₆*E_i+1,j+1; and

determine a total quantization error, or D_i,j comprising a partial tone quantization error, N_i,j.

9. The image tone quantization module of the system for producing image output of claim 8 wherein the image tone quantization module is further configured to quantize the assigned pixel tone level of each pixel, or S_i,j, in series j based on a threshold value.

10. A processor readable medium having processor executable instructions thereon which, when executed by a processor cause the processor to:

for alternate rows of pixels of a digital image having input pixel tone levels according to i rows and j columns;

quantize an assigned pixel tone level of each pixel, or S_i,j, in series j, wherein the assigned tone level, or S_i,j, comprises an input tone value, or P_i,j, and, if present, a partial tone quantization error, or N<sub>i,j−

1</sub>, from a last quantized pixel; and

determine a total quantization error, or D_i,j comprising a partial tone quantization error, or N_i,j, and remainder tone quantization error, or E_i,j, and

store the remainder tone quantization error, or E_i,j; and

for rows of pixels interposed between the alternate rows of pixels of the digital image;

quantize an assigned pixel tone level of each pixel, or S_i,j, in series j, of row i, wherein the assigned tone level, or S_i,j, comprises;

(a) an input tone value, or P_i,j;

(b) a partial tone quantization error, or N<sub>i,j−

1</sub>, from the last quantized pixel in row i, if present; and

(c) a sum of a weighted remainder tone quantization errors of two or more of the nearest neighbor pixels of the alternate rows comprising the sum;

w₂*E<sub>i−

1,j</sub>+w₅*E_i+1,j+w₆*E<sub>i+1,j−

1</sub>) and, at least one of;

(i) the sum;

w₁*E<sub>i−

1,j−

1</sub>+w₄*E<sub>i+1,j−

1</sub> and (ii) the sum;

w₃*E<sub>i−

1,j+1</sub>+w₆*E_i+1,j+1; and

determine a total quantization error, or D_i,j comprising a partial tone quantization error, N_i,j.

11. The processor readable medium having processor executable instructions thereon of claim 10 which, when executed by a processor cause the processor to quantize the assigned pixel tone level of each pixel, or S_i,j, in series j based on a threshold value.