IPWIN Function

PV-WAVE Extreme Advantage > Image Processing Toolkit User Guide > Reference A–I > IPWIN Function

IPWIN Function

Computes one of several different data windows: Blackman, Chebyshev, Hamming, Hanning, Kaiser, rectangular, or triangular.

Usage

result = IPWIN(n[, m] [, a])

Input Parameters

n—The first dimension of the window sequence.

m—(optional) The second dimension of the window sequence. If m is not given, a one-dimensional window of length n is returned.

a—(optional) A scalar float parameter used only when computing either the Kaiser or Chebyshev windows.

Returned Value

result—A 1D or 2D array containing the requested window.

Keywords

Blackman—If set, a Blackman window is returned.

Center—If set, the window is shifted such that its center is at the center of the result array.

Chebyshev—If set, a Chebyshev window is returned. If Chebyshev is set, input parameter a (a is θ0 in the Chebyshev window equation) is also required.

Hamming—If set, a Hamming window is returned.

Hanning—If set, a Hanning window is returned.

Kaiser—If set, a Kaiser window is returned. If Kaiser is set, input parameter a (a is α in the Kaiser window equation) is also required.

Rectangular—If set, a rectangular window is returned. This is also known as a boxcar window.

Triangular—If set, a triangular window is returned.

Window_Type—A scalar value (see the following table) used to specify a window type. This keyword may be used in place of the particular window keywords.

1—Rectangular

2—Triangular

3—Hanning

4—Hamming

5—Kaiser

6—Blackman

7—Chebyshev

Discussion

A listing of the applicable time domain equations is given below, where (w(n), 0 < n < N – 1) for each of the windows.

Blackman window:

Chebyshev window:

for N = 0:

for N = 1:

for N > 1:

where:

and θ0 is the IPWIN input parameter a.

Hamming window:

Hanning window:

Kaiser window:

where I0(x) is the zeroth order Bessel function of the first kind, and α is the IPWIN input parameter a.

Rectangular (or boxcar) window:

w(n) = 1, for all n.

Triangular window:

for all n.

Example

This example illustrates how to generate each of the different window types for a 128-by-128 window.

n = 128

m = 128

; Generate and view a rectangular window.

rect = IPWIN(n, m, /Rectangular, /Center)

TVSCL, rect

; Generate and view a triangular window.

tri = IPWIN(n, m, /Triangular, /Center)

TVSCL, tri

; Generate and view a Hanning window.

hann = IPWIN(n, m, /Hanning, /Center)

TVSCL, hann

; Generate and view a Hamming window.

hamm = IPWIN(n, m, /Hamming, /Center)

TVSCL, hamm

; Generate and view a Kaiser window.

kaiser = IPWIN(n, m, 0.5, /Kaiser, /Center)

TVSCL, kaiser

; Generate and view a Blackman window.

black = IPWIN(n, m, /Blackman, /Center)

TVSCL, black

; Generate and view a Chebyshev window.

cheby = IPWIN(n + 1, m + 1, 0.15, /Chebyshev, $
/Center)

TVSCL, cheby