pgmramp

Updated: 15 February 2014
Table Of Contents

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.

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.

ppmrainbow does something similar to what pgmramp does, but for color. The image fades between two colors of your choice.

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.