Function iacos

Synopse

Create a cosine wave image.

  • f = iacos(s, t, theta, phi)
    • f: Image.
    • s: Image. size: [rows cols].
    • t: Image. Period: in pixels.
    • theta: Double. spatial direction of the wave, in radians. 0 is a wave on the horizontal direction.
    • phi: Double. Phase
1. import numpy as np
2. 
3. def iacos(s, t, theta, phi):
4.     r, c = np.indices(s)
5.     tc = t / np.cos(theta)
6.     tr = t / np.sin(theta)
7.     f = np.cos(2*np.pi*(r/tr + c/tc) + phi)
8.     return f

Description

Generate a cosine wave image of size s with amplitude 1, period T, phase phi and wave direction of theta. The output image is a double array.

Examples

Example 1

1. from ia636 import iacos, ianormalize
2. 
3. f = iacos([128,256], 100, pi/3, 0)
4. adshow(ianormalize(f, [0,255]))

Equation

  • is the direction of the cosine wave.
  • is the wave period, in number of pixels.
  • and are the period or wave length in the vertical and horizontal directions, respectively, in number of pixels.
  • and are the number of image rows and columns, respectively.
  • and are the normalized frequency in the horizontal and vertical directions, respectively, in cycles per image dimension.

See Also

  • iacosdemo -- Illustrate discrete cosine wave and its DFT showing its periodic nature.