pix-bw — combine pix color planes into a bw black and white image
pix-bw [-s squaresize] [-w width] [-n height] [
[-e ntsc|crt|hdtv|hdr|avg]
[
[ -R r_weight]
[ -G g_weight]
[ -B b_weight] ] ] [-o out.bw] [
[<]in.pix] > out.bw
pix-bw will combine or select the color planes of a pix(5) format file from its standard input and produce a black and white bw(5) file on its standard output.
The
-w file_width
flag specifies the width of each scanline in the input file, in pixels.
The
-n file_height
flag specifies the height in scanlines of the input file.
They are set to the same value using
-s squarefilesize.
By default all three colors are weighted equally.
The
-e type
flag can be used to specify a standard weighting scheme;
the
type
choices include:
Weighting used is based on the NTSC primaries and white alignment. Conforming with Rec.ITU-R BT.601-7, this uses 0.299/0.587/0.114 RGB weights. This gives a simplified linear conversion of perceived luminance that reflects human physiological sensitivity to green and least to blue.
Weighting scheme matches "historic" CRT phosphor chromaticities and a D6500 white alignment. Uses 0.26/0.66/0.08 RGB weights.
Weighting scheme matches "modern" HDTV display chromacities. Uses 0.2126/0.7152/0.0722 RGB weights per Rec.ITU-R BT.709
Weighting scheme matches high dynamic range (HDR) chromacities. Uses 0.2627/0.6780/0.0593 RGB weights per Rec.ITU-R BT.2020
Weighting scheme simply takes the average of all three values (i.e., R + G + B / 3.0).
Individual color plane(s) can be selected via the
-R#, -G#,
and
-B#
options.
The value used with each flag
will be treated as a weight
to be applied to that color.
If 0 is supplied by the user for weights, then the weights assigned are 1.0 divided by the number of colors selected.
pix-bw -R0.0 -B0.0 < file.pix > file.bw
will equally blend the red and blue color planes; because -G is omitted, the green color plane is not considered. (Had "-G0.0" been included in this example, the three colors would have been weighted equally, as in the default condition.)
pix-bw -R0.3 -G0.6 -B0.1 < file.pix > file.bw
applies weights close to the -ntsc flag.