CGLOGSCL
This is a utility routine to perform a logarithmic transformation
on an image. The shape of the transformation is similar to the gamma
curve (see cgGmaScl), except that the shape of the gamma curve is
variable, while the log curve is fixed. The function is used to improve
contrast in images. The equation being implemented before scaling between
OMIN and OMAX is as follows::
output = constant * Log(1 + double(input))
Categories
Image Processing
Returns
A byte scaled image is returned.
Params
image: in, required
The image to be scaled. Written for 2D images, but arrays of any size are treated alike.
Keywords
constant: in, optional, type=float, default=1.0
A contant value by which the log result is multiplied.
max: in, optional
Any value in the input image greater than this value is set to this value
before scaling.
min: in, optional
Any value in the input image less than this value is set to this value
before scaling.
negative, in, optional, type=boolean, default=0
If set, the "negative" of the result is returned.
omax: in, optional, type=byte, default=255
The output image is scaled between OMIN and OMAX.
omin: in, optional, type=byte, default=0
The output image is scaled between OMIN and OMAX.
Examples
Examples of compression stretching::
cgLoadCT, 0 ; Gray-scale colors.
image = cgDemoData(22) ; Load image.
cgImage, image ; No contrast.
cgImage, cgLogScl(image) ; Improved contrast.
Author
FANNING SOFTWARE CONSULTING::
David W. Fanning
1645 Sheely Drive
Fort Collins, CO 80526 USA
Phone: 970-221-0438
E-mail: [email protected]
Coyote's Guide to IDL Programming: http://www.idlcoyote.com
History
Change History::
Written by: David W. Fanning, 27 March 2015. DWF.
Copyright
Copyright (c) 2015, Fanning Software Consulting, Inc.