remove ever other row from a PAM/PNM image
see also :
pamstretch - pnmscale
[-takeodd] [-takeeven] N
You can use the
minimum unique abbreviation of the options. You can use two
hyphens instead of one. You can separate an option name from
its value with white space instead of an equals sign.
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Removes all the even-numbered or odd-numbered rows from the
input PNM or PAM image. Specify which with the
-takeeven and -takeodd options.
This can be
useful if the image is a video capture from an interlaced
video source. In that case, each row shows the subject 1/60
second before or after the two rows that surround it. If the
subject is moving, this can detract from the quality of the
resulting image is half the height of the input image, you
will then want to use pamstretch or pnmscale
to restore it to its normal height:
myimage.ppm | pamstretch -yscale=2 >newimage.ppm
Take the odd-numbered rows from
the input and put them in the output. The rows are numbered
starting at zero, so the first row in the output is the
second row from the input. You cannot specify both
-takeeven and -takeodd.
Take the even-numbered rows
from the input and put them in the output. The rows are
numbered starting at zero, so the first row in the output is
the first row from the input. This is the default. You
cannot specify both -takeeven and
put by Bryan
Henderson in the public domain in 2001