NAME
pgmramp - generate a grayscale ramp
SYNOPSIS
pgmramp {-lr|-tb|-rectangle|-ellipse|-diagonal} [-maxval=maxval] width height
All options can be abbreviated to their shortest unique prefix. You may use two hyphens instead of one to designate an option. You may use either white space or an equals sign between an option name and its value.
DESCRIPTION
This program is part of Netpbm(1).
Generates a graymap of the specified size containing a black-to-white ramp. These ramps are useful for multiplying with other images, using pamarith.
The ramp is linear in brightness, not intensity. I.e. the gamma-corrected sample values in the PGM rise linearly with distance from the corner of the image. If you want a ramp that is linear in light intensity, use pnmgamma with pgmramp.
Options let you choose the shape of the ramp (left to right, inside out, etc.). You can use pamflip to get more shapes. For example, the -lr option gives you a left to right ramp and
$ pgmramp -lr 100 100 | pamflip -lr
gives you a right to left ramp.
To generate a simple ramp of all the values from 0 to maxval, and not necessarily a graphic image, use pamseq(1).
ppmrainbow does something similar to what pgmramp does, but for color. The image fades between two colors of your choice.
OPTIONS
In addition to the options common to all programs based on libnetpbm (most notably -quiet, see Common Options ), pgmramp recognizes the following command line options:
You must specify exactly one of the ramp type options.
|
-lr |
A left to right ramp. Black on the left; white on the right. | ||
|
-tb |
A top to bottom ramp. Black on top; white on the bottom. |
-rectangle
An outside-in rectangular ramp. It is black around the edges and white in the center.
-ellipse
An outside-in elliptical ramp. It is black around the edge and white in the center.
-diagonal
A ramp from top left corner diagonally down to bottom right. Black at the top left; white at the bottom right.
This option was new in Netpbm 10.66 (March 2014).
-maxval=maxval
The maxval for the generated image. Default is 255.
This option was
new in Netpbm 10.1 (June 2002). Before that, the maxval
is always 255.
SEE ALSO
pamflip(1), pamarith(1), pnmgamma(1), pamseq(1), ppmrainbow(1), pamgradient(1), pgm(1)
AUTHOR
Copyright (C) 1989 by Jef Poskanzer.
DOCUMENT SOURCE
This manual page was generated by the Netpbm tool ’makeman’ from HTML source. The master documentation is at