Note: This page has been translated by MathWorks. Please click here

To view all translated materials including this page, select Japan from the country navigator on the bottom of this page.

To view all translated materials including this page, select Japan from the country navigator on the bottom of this page.

Image pyramid reduction and expansion

`B = impyramid(A,direction)`

If `A`

is *m*-by-*n* and `direction`

is `'reduce'`

,
the size of `B`

is `ceil(M/2)`

-by-`ceil(N/2)`

.
If `direction`

is `'expand'`

, the
size of `B`

is `(2*M-1)`

-by-`(2*N-1)`

.

Reduction and expansion take place only in the first two dimensions.
For example, if `A`

is 100-by-100-by-3 and `direction`

is `'reduce'`

,
then `B`

is 50-by-50-by-3.

`impyramid`

uses the kernel specified on page
533 of the Burt and Adelson paper:

$$w=\left[\frac{1}{4}-\frac{a}{2},\frac{1}{4},a,\frac{1}{4},\frac{1}{4}-\frac{a}{2}\right]$$, where $$a\text{=0}\text{.375}$$. The parameter *a* is
set to `0.375`

so that the equivalent weighting function
is close to a Gaussian shape. In addition, the weights can be readily
applied using fixed-point arithmetic.

[1] Burt and Adelson, "The Laplacian Pyramid
as a Compact Image Code," *IEEE Transactions on Communications*,
Vol. COM-31, no. 4, April 1983, pp. 532-540.

[2] Burt, "Fast Filter Transforms for Image
Processing," *Computer Graphics and Image Processing*,
Vol. 16, 1981, pp. 20-51

Was this topic helpful?