FB-BW(1)

NAME

fb-bw - save a framebuffer image in a black and white bw file

On this page

SYNOPSIS
DESCRIPTION
OPTIONS
EXAMPLES
SEE ALSO
AUTHOR
COPYRIGHT
BUG REPORTS

SYNOPSIS

fb-bw [-h] [-i] [-F framebuffer] [-X scr_xoff] [-Y scr_yoff] [-s squaresize] [-w width] [-n height] [file.bw]

fb-bw saves a region of a framebuffer display as a black and white bw(5) format file. The conversion is performed by computing an equal blending of the red, green, and blue channels. For more complex conversions, use fb-pix(1) and pix-bw(1).

By default, a first quadrant coordinate system is used (origin in the lower left of the screen), and the saved area starts from this origin.

OPTIONS

-F framebuffer: Explicitly specify the framebuffer device. If not set, the environment variable FB_FILE is used to select the display device (see brlcad(1)). If FB_FILE is also not set, the default device for the system will be used.
-s squaresize: Set both the output file width and height to the given squaresize. The default size is 512x512 pixels.
-w width: Set the output file width.
-n height: Set the output file height.
-X scr_xoff: Set the starting X coordinate (offset) on the screen.
-Y scr_yoff: Set the starting Y coordinate (offset) on the screen.
-i: Use a fourth quadrant coordinate system (origin at the upper left corner of the screen) instead of the default first quadrant (origin at the lower left). This changes both the origin offset coordinates and the storage order.
-h / -?: Print a help message and exit.

EXAMPLES

Example 1. Grab the current framebuffer and threshold it into a silhouette

fb-bw -F /dev/X -s 1024 | bwmod -m 4 -c | bw-fb -s 1024

Reads the entire 1024x1024 framebuffer, converts it to a single grayscale channel, brightens and clamps it with bwmod(1) to produce a high-contrast silhouette, and displays the result back on the framebuffer with bw-fb(1).

Example 2. Save a specific region of the framebuffer to a file

fb-bw -X 256 -Y 256 -w 512 -n 512 region.bw

Captures a 512x512 region starting at screen offset (256, 256) from the default framebuffer and writes the grayscale result to region.bw.