Symbols in form of PNG images enable to choose easily symbols in d.vect
and in wx.psmap dialogs. It is necessary to keep images synchronized with
symbols from ./lib/symbol/symbol/ directories.

How to create new symbol image:
----------------------------------
You can use following script (requires Inkscape), run script in symbol group
directory (e.g. ./lib/symbol/symbol/basic) within a GRASS session.
Optipng will try to make the file as small as possible.

#!/bin/sh
DIR="$(basename $PWD)"
PSMAP_FILE=tmp.psmap
PS_FILE=tmp.ps
PNG_OUT=png_out

rm -r "$PNG_OUT"
mkdir "$PNG_OUT"
for SYMBOL in *
do
    if [ -f "$SYMBOL" ]
    then
        echo -e "border none\npoint 50% 50%\n  symbol $DIR/$SYMBOL\n  end\nend" > "$PSMAP_FILE"
        ps.map input="$PSMAP_FILE" output="$PS_FILE"
        inkscape -f "$PS_FILE" --export-png="$PNG_OUT/$SYMBOL.png" -D -h=30
        
        rm "$PSMAP_FILE" "$PS_FILE"

        #optipng -o5 "$PNG_OUT/$SYMBOL.png"
    else
        echo "$SYMBOL is not regular file"
    fi
done

Image should have 30x30 px to be displayed correctly in GUI dialog. If the symbol
has different width and height, you are supposed to correct it (for example
in Gimp see Image -> Canvas size). Also consider where the reference point of symbol
is placed (see e.g. offbox_ne, offbox_ns symbols).