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Effective Color Interpolation in CCD Color Filter Arrays Using Signal Correlation

作者 :Soo-Chang Pei, Io-Kuong Tam

出處 : IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY, VOL. 13, NO. 6, JUNE 2003

報告人 :董文豪日期 :2011/05/04

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Outline

Introduction Color Filter Arrays ( CFA ) Conventional interpolation methods

BilinearEdge-sensing interpolation

Proposed interpolation method Experiment results

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Introduction

The authors propose an effective color filter array (CFA) interpolation method for digital still cameras using a simple image model that correlates the R,G,B channels.

A low-complexity interpolation method to improve the image quality.

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Color Filter Arrays -CFA ( 1/2 )

Three-CCD structure for a DSC.

Single-CCD structure for a DSC.

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Color Filter Arrays -CFA ( 1/2 )

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Conventional interpolation methods ( 1/4 )

Bilinear

R7

G3

G6

G11

B2 B4

B12B10

G8

R1

R5

R13

R9

G’7=

G3+G6+G8+G11 4

R’3= R1+R7 2

B’7=B2+B4+B10+B12 4

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Conventional interpolation methods ( 2/4 )

Bilinear

H H

H H

H H

H H

L L

L

L L

L L

L

Vertical edge patterns

An obvious error is produced and the edge pattern is destroyed.

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∆H=|G6 - G8| , ∆V=|G3 – G11|,

If ( ∆H < T ) and ( ∆V > T ) ,

G’7 = G’7H ,

else if ( ∆V < T ) and ( ∆H > T ) ,

G’7 = G’7V

else

G’7 = G’7A

R1

B2 G3 B4

R5 G6 R7 G8 R9

B10 G11 B12

R13

G3

G11

G8G6

Conventional interpolation methods ( 3/4 )

Edge-sensing interpolation ( G )

R13

R1 G’7H=

G’7V=

G’7A=

G6 + G8 2

G3 + G11 2

G3 + G6 + G8 + G11 4

B12

B4

R9R7R5

B2

B10

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Conventional interpolation methods ( 4/4 )

Edge-sensing interpolation ( R,B )

G3

G6 G8

G11

R1

R5

R13

R9

G11

G8

G3B2 B4

B12B10

R7G6

HB = B G

, HR

=

R G

B’3 = B 2 G’2

( + ) /2B 4 G’4 ( )

G3 2

B’7 = ( + + + ) /4B 2 G’2

B 4 G’4

B10 G’10

B 12 G’12

( )G’7 4

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Proposed interpolation method ( 1/3 )

Above two methods use only the existing G channel neighborhood information to find the missing G values.

There is a high correlation between the R,G,B channels.

The G channel can take advantage of the R and B information.

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Proposed interpolation method ( 2/3 )

G channel image KR channel image KB channel image

KR = G – R

KB = G – B

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Proposed interpolation method ( 3/3 )

G3

R9R5 R7

R1

R13

B2 B4

B10 B12G11

G6 G8

G’7 =R7+( K’R3 + K’R6 + K’R8 + K’R11 ) /4

= R7 + ［ G3 - (R7+R1) +

G6 - (R7+R5) + G8 - (R7+R9) +

G11- (R7+R13)］

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12121212

= R7+ ( G3+G6+G8+G11 )

- ( R1+R5+R9+R13 )

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G Channel InterpolationR,B Channel Interpolation

R’3 = G3 - ( K’R1 + K’R7 )12

B’7=

G’7- ( K’B2+ K’B4+ K’B10+ K’B12 )14

KR = G – R

KB = G – B

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Experiment results ( 1/2 )

PSNR OF THE INTERPOLATED RESULTS

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Experiment results ( 2/2 )

COMPLEXITY COMPARISON

G’7 = R7+ ( G3+G6+G8+G11 )

- ( R1+R5+R9+R13 )

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The end