IPALOG Function (PV-WAVE Extreme Advantage)
Computes the natural logarithm of an image, excluding zero values.
Usage
result = IPALOG(image)
Input Parameters
image—An array of any data type except string.
Returned Value
result—The logarithm to the base e (the natural log) of image, excluding zero values. For double-precision floating-point and complex values result is returned with the same data type. All other valid data types are converted to single-precision floating-point and result is returned as a floating-point data type.
Keywords
None.
Discussion
The IPALOG function is useful for displaying images with wide dynamic range and is defined as follows:
y = logex
Values in image which are zero are left as zero.
The IPALOG function handles complex numbers in the following way:
IPALOG(image) ≡ Complex(loge(|image|, arctan(image)))
note | When error messages regarding the handling of zero values in the input are not wanted, you should use the IPALOG function instead of the PV‑WAVE ALOG function. |
Example
; Generate a test image.
x = DIST(256)
; Take the fast Fourier transform of x.
f = FFT(x, -1)
; Display the log magnitude of the image FFT, with zero values
; retained as zeros.
TVSCL, IPALOG(ABS(f))
See Also
In the PV‑WAVE Reference: ALOG
