Interpolation of RGB components in Bayer CFA images

CEG4311Eric Dubois

Demosaicking of Bayer-sampled color images

Problem: Most digital color cameras, capture only one color component at each spatial location. The remaining components must be reconstructed by interpolation from the captured samples. Objective: Develop algorithms to interpolate each color plane (called demosaicking) with best quality reconstruction, and with minimal computational complexity.

Construction of color image from color planes

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Lighthouseoriginal

Lighthousered original

Lighthousegreen original

Lighthouseblue original

Formation of Color planes

Lighthousered subsampled

Lighthousegreen subsampled

Lighthouseblue subsampled

LighthouseBayer CFA image

Color plane interpolation

GA

GB

GL GR

)(4

1ABRLI GGGGG

GI

Green channel: bilinear interpolation

Color plane interpolation

)(4

1SESWNENWC RRRRR

RC

Red channel: bilinear interpolation

RNW RNE

RSW RSE RS

SESWS RRR 2

1

Lighthousered interpolated

Lighthousegreen interpolated

Lighthouseblue interpolated

LighthouseInterpolated color image

Lighthouseoriginal

Can we do better?

Color planes have severe aliasing. Better interpolation of the individual planes has little effect.

Lighthousered interpolatedwith bilinear interpolator

Lighthousered interpolatedwith bicubic interpolator

Can we do better?

Color planes have severe aliasing. Better interpolation of the individual planes has little effect.

We could optically prefilter the image (blur it) so that aliasing is less severe.

Lighthousered interpolatedwith bilinear interpolator

Lighthouseprefiltered red interpolatedwith bilinear interpolator

LighthouseInterpolated color image

LighthousePrefiltered Interpolated color image

Lighthouseoriginal

LighthouseInterpolated color image with new frequency domain method