OpenGL Insights

460 V Transfers

This scheme uses slightly different vectors for the computation of chromatic val-

ues to make the resulting math simple:

Y = (R + 2G + B)/4,

C

o

= 0.5 + (2R − 2B)/4,

C

g

= 0.5 + (−R + 2G − B)/4.

R = 2Y(2C

o

− C

g

),

G = 2YC

g

,

B = 2Y(2 − 2C

o

− C

g

).

Like the YC

o

C

g

-S, this scheme addresses the problems of quantization in the

non-scaled YC

o

C

g

mode; however, it’s not a quality improvement over the YC

o

C

g

-S

scheme, as the peak signal-to-noise ratio (PSNR) metrics indicate as well.

31.5 Comparison

The compression schemes have been tested on a few sample scenes using a visual

test together with the commonly used PSNR metrics for comparison. Figure 31.2

shows ...