gistfile1.sh

# make a heatmap legend for ploticus scatterplot heatmaps
# using colors.png as a palette, first pixel of each line
# > echo png2html > /tmp/.png.$$
# > png2html colors.png /tmp/.png.$$ test_png.html 2
# > perl -nle '/#(......)/ && print "$1"' test_png.html > colors.txt

legentry () {
    a="xrgb($1)"; b=$1; c="$2+"
    if [ ${b:0:1} = "-" ]; then a="${b:1}"; fi
    if [ "$3" ]; then c="$2-$3"; fi
    cat <<LEG
#proc legendentry
 sampletype: color
 details: $a
 tag: $2
 label: $c
LEG
}

end=145
lines=$(cat colors.txt | wc -l)
scale=$((echo scale=5; echo $lines/$end)|bc)
for i in $(seq $end -10 10); do
    kk=$((echo "($i*$scale)/1")|bc)
    j=$(sed -ne ${kk}p < colors.txt)
    legentry $j $i $last
    last=$((i-1))
done
legentry "35343D" 1 $last
legentry "-black" 0