Multi-Level Surround Error Diffusion

• US 20100245924A1
• 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 8,274,705 B2
• Time in Patent Office: Days
• US Class Current: 358/3.40
• 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 diffusing tone quantization error of a digital image comprising:

receiving a digital image having input pixel tone levels for one or more color channels 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, per color channel, in series j based on an integer downsizing, 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 for each pixel in series j, and per color channel, a total quantization error, or D_i,j, based on the assigned pixel tone level of the pixel, or S_i,j, and the quantized assigned pixel tone level of the pixel, or Q_i,j, wherein the total quantization error, or D_i,j,comprises a partial tone quantization error, or N_i,j, and a remainder tone quantization error, or E_i,j, and

storing, per color channel, 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, per color channel, in series j based on an integer downsizing, 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_i+1,j+1) 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, for each pixel in series j, and per color channel, a total quantization error, or D_i,j, based on the assigned pixel tone level of the pixel, or S_i,j, and the quantized assigned pixel tone level of the pixel, or Q_i,j, wherein the total quantization error, or D_i,j ,comprises a partial tone quantization error, or N_i,j,.

2. The method of diffusing tone quantization error of a digital image of claim 1 wherein the integer downsizing of an assigned pixel tone level comprises:

dividing the assigned pixel tone level of each pixel, or S_i,j, by 2^B+1 to generate a quotient having an integer component;

adding unity to the integer component of the quotient to generate a quantized tone value; and

testing to maintain the quantized tone value at least a value of unity and no more a value than 2^B; and

wherein if the assigned pixel tone level of each pixel, or S_i,j, is an eight-bit integer, then B=4, and the quantized pixel tone level, or Q_i,j, is a four-bit integer.

3. The method of diffusing tone quantization error of a digital image of claim 2 wherein the total quantization error, or D_i,j ,is assigned the value of:

the assigned pixel tone level of each pixel, or S_i,j, plus (2^B+1), and less the value of the product of quantized pixel tone level, or Q_i,j, and (2^B+1).

4. The method of diffusing tone quantization error of a digital image of claim 1 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, based on an integer downsizing, 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.

5. The method of diffusing tone quantization error of a digital image of claim 1 wherein w₁=⅛

;

w₂= 2/8;

w₃=⅛

;

w₄=⅛

;

w₅= 2/8; and

w₆=⅛

.

6. A system for producing image output comprising:

a image tone quantization module configured to;

input a digital image having input pixel tone levels for one or more color channels according to i rows and j columns;

for alternate rows of pixels of the digital image;

quantize an assigned pixel tone level of each pixel, or S_i,j, per color channel, in series j based on an integer downsizing, 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

determine for each pixel in series j, and per color channel, a total quantization error, or D_i,j, based on the assigned pixel tone level of the pixel, or S_i,j, and the quantized assigned pixel tone level of the pixel, or Q_i,j, wherein the total quantization error, or D_i,j ,comprises a partial tone quantization error, or N_i,j, and a remainder tone quantization error, or E_i,j, and

store, per color channel, 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, per color channel, in series j based on an integer downsizing, 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_i+1,j+1) 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<sub>i−

1,j+1</sub>; and

determine, for each pixel in series j, and per color channel, a total quantization error, or D_i,j, based on the assigned pixel tone level of the pixel, or S_i,j, and the quantized assigned pixel tone level of the pixel, or Q_i,j, wherein the total quantization error, or D_i,j ,comprises a partial tone quantization error, or N_i,j,.

7. The image tone quantization module of the system for producing image output of claim 6 wherein the image tone quantization module processing the integer downsizing of an assigned pixel tone level is configured to:

divide the assigned pixel tone level of each pixel, or S_i,j, by 2^B+1 to generate a quotient having an integer component;

add unity to the integer component of the quotient to generate a quantized tone value; and

test to maintain the quantized tone value at least a value of unity and no more a value than 2^B; and

wherein if the assigned pixel tone level of each pixel, or S_i,j, is an eight-bit integer, then B=4, and the quantized pixel tone level, or Q_i,j, is a four-bit integer.

8. The image tone quantization module of the system for producing image output of claim 7 wherein the image tone quantization module processing the integer downsizing of an assigned pixel tone level is further configured to assign the total quantization error, or D_i,j, the value of:

the assigned pixel tone level of each pixel, or S_i,j, plus (2^B+1), and less the value of the product of quantized pixel tone level, or Q_i,j, and (2^B+1).

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

input a digital image having input pixel tone levels for one or more color channels according to i rows and j columns;

for alternate rows of pixels of the digital image;

quantize an assigned pixel tone level of each pixel, or S_i,j, per color channel, in series j based on an integer downsizing, 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

determine for each pixel in series j, and per color channel, a total quantization error, or D_i,j, based on the assigned pixel tone level of the pixel, or S_i,j, and the quantized assigned pixel tone level of the pixel, or Q_i,j, wherein the total quantization error, or D_i,j ,comprises a partial tone quantization error, or N_i,j, and a remainder tone quantization error, or E_i,j, and

store, per color channel, 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, per color channel, in series j based on an integer downsizing, 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_i+1,j+1) 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<sub>i−

,j+1</sub>; and

determine, for each pixel in series j, and per color channel, a total quantization error, or D_i,j, based on the assigned pixel tone level of the pixel, or S_i,j, and the quantized assigned pixel tone level of the pixel, or Q_i,j, wherein the total quantization error, or D_i,j ,comprises a partial tone quantization error, or N_i,j,.

10. The processor readable medium having processor executable instructions thereon of claim 9 which, when executed by a processor cause the processor to:

divide the assigned pixel tone level of each pixel, or S_i,j, by 2^B+1 to generate a quotient having an integer component;

add unity to the integer component of the quotient to generate a quantized tone value; and

test to maintain the quantized tone value at least a value of unity and no more a value than 2^B; and

wherein if the assigned pixel tone level of each pixel, or S_i,j, is an eight-bit integer, then B=4, and the quantized pixel tone level, or Q_i,j, is a four-bit integer.

11. The processor readable medium having processor executable instructions thereon of claim 10 which, when executed by a processor cause the processor to assign the total quantization error, or D_i,j, the value of:

the assigned pixel tone level of each pixel, or S_i,j, plus (2^B+1), and less the value of the product of quantized pixel tone level, or Q_i,j, and (2^B+1).