Page 154 -

3.5 Pyramids and wavelets 133

coarse l = 2

medium l = 1

fine l = 0

Figure 3.32 A traditional image pyramid: each level has half the resolution (width and height), and hence a
quarter of the pixels, of its parent level.

1 ¼ Ǫ ¼ 1
16 16 ǩ ½ ¾ ½ ǩ

1 1
16 ¼ Ǫ ¼ 16 ǩ ½ ¾ ½ ǩ

(a) (b)

Figure 3.33 The Gaussian pyramid shown as a signal processing diagram: The (a) analysis and (b) re-synthesis
stages are shown as using similar computations. The white circles indicate zero values inserted by the ↑ 2
upsampling operation. Notice how the reconstruction filter coefficients are twice the analysis coefficients. The
computation is shown as flowing down the page, regardless of whether we are going from coarse to fine or vice
versa.