[GRASSLIST:5052] one bit deep PNGs

GRASS GRASS user
1

How does one get 1 bit deep PNGs? I only draw with black on white, but
$ d.mon stop=PNG
$ convert -monochrome map.png shichengst1.png
$ xli shichengst1.png
shichengst1.png is a 640x480 8 bit deep grayscale PNG image with an
alpha channel, background = #ff
GRASS 5.7.0

2

How does one get 1 bit deep PNGs? I only draw with black on white, but
$ d.mon stop=PNG
$ convert -monochrome map.png shichengst1.png
$ xli shichengst1.png
shichengst1.png is a 640x480 8 bit deep grayscale PNG image with an
alpha channel, background = #ff
GRASS 5.7.0

maybe with pnmquant? (NetPBM program)

pngtopnm file_8bit.png | pnmquant [options] | pnmtopng > file_1bit.png

Hamish

3

Thanks. pnmquant has some magic number problem. However I succeeded
in debloating my already black and white PNG file with
$ file ...; ls ...
map.png: PNG image data, 640 x 480, 8-bit colormap, non-interlaced
-rw-r--r-- 1 5510 2004-12-05 13:25 map.png
$ pngtopnm map.png|pnmcrop|pnmtopng > file_1bit.png
file_1bit.png: PNG image data, 635 x 395, 1-bit colormap, non-interlaced
-rw-r--r-- 1 2848 2004-12-07 05:22 file_1bit.png