FBCMAP(1)

NAME

fbcmap - load a built-in color map onto a framebuffer

On this page

SYNOPSIS
DESCRIPTION
OPTIONS
EXAMPLES
SEE ALSO
AUTHOR
COPYRIGHT
BUG REPORTS

SYNOPSIS

fbcmap [-h] [-F framebuffer] [-{sS} squarescrsize] [-{wW} scr_width] [-{nN} scr_height] [map_number]

fbcmap writes one of several built-in color maps to a framebuffer. When invoked with no map_number argument, or with a map_number of 0, the standard linear (identity) color map is loaded. Other map numbers select alternative mappings such as a photographic negative, film correction, gamma correction, or solid calibration fields.

Note that fbcmap is deprecated and scheduled for removal; for general gamma correction use fbgamma(1) instead.

OPTIONS

-h: Print a usage summary listing the available maps, then exit.
-F framebuffer: Specify the framebuffer device. If not given, the FB_FILE environment variable is used (see brlcad(1)); if that is unset the default device for the system is used.
-s squarescrsize: Set both the width and height of the framebuffer to squarescrsize pixels.
-S squarescrsize: Same as -s.
-w scr_width: Set the framebuffer display width to scr_width pixels.
-W scr_width: Same as -w.
-n scr_height: Set the framebuffer display height to scr_height pixels.
-N scr_height: Same as -n.

If no size options are given, the requested framebuffer size is the default for the selected device (typically 512x512 pixels).

The optional map_number argument selects the color map to load:

0: Linear (identity) color map (default).
1: Reverse-linear (photographic negative) map.
2: Corrected for Polaroid 809/891 print film.
3: Linear map with the low 100 entries set to black.
4: Middle range amplified (shifted up by 64) to boost dim pictures; entry 0 stays black and the top entries clamp to full intensity.
5: Gamma-correcting map from the University of Utah Alpha_1 project.
6: Color deltas: mostly black, with full-intensity colors at multiples of 32 (white 0, magenta 32, red 64, yellow 96, green 128, cyan 160, blue 192).
8: Ikcmap 8 false-color map.
9: Ikcmap 9 false-color map.
10: Solid black.
11: Solid white.
12: 18% neutral grey.

Maps 10 through 12 are useful for adjusting a camera to a uniform field without disturbing image memory.

EXAMPLES

Example 1. Display a negative of an existing image

pix-fb -F /dev/fb0 moss.pix
fbcmap -F /dev/fb0 1

Load an image onto a framebuffer with pix-fb(1), then load map 1 so the displayed pixels appear as a photographic negative without altering the stored pixel values. Loading map 0 afterward restores normal appearance.

Example 2. Calibrate against a uniform 18% grey field

fbcmap -s 1024 12

Open (or size) the framebuffer to 1024x1024 and remap every pixel to 18% neutral grey, a common reference value when adjusting a camera or monitor.