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PIX-BW(1)

NAME

pix-bw - convert a color pix image into a black and white bw image

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SYNOPSIS

pix-bw [-s squaresize] [-w width] [-n height] [-e ntsc|crt|hdtv|hdr|avg] [-R red_weight] [-G green_weight] [-B blue_weight] [-o out_file.bw] [[<] file.pix] [> out_file.bw]

DESCRIPTION

pix-bw combines or selects the color planes of a pix(5) format image, read from standard input or from a named file, and produces an 8-bit greyscale bw(5) image on standard output.

By default the red, green, and blue planes are weighted equally. A standard weighting scheme may be chosen with -e, or arbitrary per-plane weights may be specified with -R, -G, and -B. Selecting only a subset of the -R, -G, and -B options computes the result from just those planes.

If the output is written to a named file with -o while standard output is also redirected or piped, the same bw(5) image is written to both destinations.

OPTIONS

-s squaresize

Set both the width and height of the input image to squaresize pixels.

-w width

Set the width of each scanline of the input image, in pixels.

-n height

Set the height of the input image, in scanlines.

-e type

Use a standard luminance weighting scheme. type may be one of: ntsc (Rec. ITU-R BT.601-7 NTSC primaries, weights 0.299/0.587/0.114); crt (historic CRT phosphors with D6500 white, weights 0.26/0.66/0.08); hdtv (Rec. ITU-R BT.709, weights 0.2126/0.7152/0.0722); hdr (Rec. ITU-R BT.2020, weights 0.2627/0.6780/0.0593); avg (simple average of the three planes).

-R red_weight

Select the red plane and apply red_weight to it.

-G green_weight

Select the green plane and apply green_weight to it.

-B blue_weight

Select the blue plane and apply blue_weight to it. If a weight of 0 is supplied to any of -R, -G, or -B, the selected planes are instead weighted equally as 1.0 divided by the number of planes selected.

-o out_file.bw

Write the output to the named bw(5) file instead of (or in addition to) standard output.

-h, -?

Print a usage message and exit.

EXAMPLES

Example 1. Convert a color image to greyscale using NTSC luminance weighting
pix-bw -e ntsc < image.pix > image.bw

Produces a perceptually weighted greyscale bw(5) image, giving green the most influence and blue the least, matching standard NTSC luminance.

Example 2. Extract a single color plane
pix-bw -G1.0 -w 512 -n 512 scene.pix | bw-pix > green.pix

Selects only the green plane of a 512x512 image and pipes the resulting bw(5) image through bw-pix(1) to view the isolated green channel as a greyscale pix(5) image.

SEE ALSO

brlcad(1), bw-pix(1), pix(5), bw(5)

AUTHOR

BRL-CAD Team

This software is Copyright (c) 1989-2026 by the United States Government as represented by U.S. Army Research Laboratory.

BUG REPORTS

Reports of bugs or problems should be submitted via electronic mail to devs@brlcad.org