Linux Commands Examples

A great documentation place for Linux commands

ppmtopgm

convert a portable pixmap into a portable graymap


see also : pgmtoppm - ppmtorgb3 - rgb3toppm - ppmdist

Synopsis

ppmtopgm [ppmfile]


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examples

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pnmmerge giftopnm < ${fich}.gif | ppmtopgm | pgmmerge pgmenhance -1 | pnmmerge pnmscale 2 | pgmmerge pgmtopbm | ppmmerge ppmtogif > ${fich}_d.gif
pnmmerge giftopnm < ${fich}.gif | ppmtopgm | pgmmerge pgmenhance -1 | pnmmerge pnmscale 2 | pgmmerge pgmtopbm | ppmmerge ppmtopict > ${fich}_d.pict
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*PPM* )
ppmtopgm "$file"
exit 0
;;
esac
exit -1
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pngtopnm $< | pnmscale 4 | pnmconvol $(srcdir)/../herds/convol11.pnm |\
ppmtopgm | pnmdepth 255 | \
pnmtops -noturn -width 100 -height 100 > $@ || rm -f $@
%.ps: $(srcdir)/../herds/%.png $(srcdir)/../herds/convol5.pnm
pnmconvol $(srcdir)/../herds/convol5.pnm | ppmtopgm | \
pnmdepth 255 | pnmtops -width 100 -height 100 -noturn > $@ || rm -f $@
%.ps: $(srcdir)/../screen/%.png
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pngtopnm $< | pnmscale 4 | pnmconvol $(srcdir)/../herds/convol11.pnm |\
ppmtopgm | pnmdepth 255 | \
pnmtops -noturn -width 100 -height 100 > $@ || rm -f $@
%.ps: $(srcdir)/../herds/%.png $(srcdir)/../herds/convol5.pnm
pnmconvol $(srcdir)/../herds/convol5.pnm | ppmtopgm | \
pnmdepth 255 | pnmtops -width 100 -height 100 -noturn > $@ || rm -f $@
%.ps: $(srcdir)/../screen/%.png

description

Reads a portable pixmap as input. Produces a portable graymap as output. The output is a "black and white" rendering of the original image, as in a black and white photograph. The quantization formula used is .299 r + .587 g + .114 b.

Note that although there is a pgmtoppm program, it is not necessary for simple conversions from pgm to ppm , because any ppm program can read pgm (and pbm ) files automatically. pgmtoppm is for colorizing a pgm file. Also, see ppmtorgb3 for a different way of converting color to gray. And ppmdist generates a grayscale image from a color image, but in a way that makes it easy to differentiate the original colors, not necessarily a way that looks like a black and white photograph.

quote

Cold-hearted orb that rules the night
Removes the colors from our sight
Red is gray, and yellow white
But we decide which is right
And which is a quantization error.


see also

pgmtoppm , ppmtorgb3 , rgb3toppm , ppmdist ,ppm,pgm


author

Copyright (C) 1989 by Jef Poskanzer.

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