#!/bin/bash
#
# output all 256 colors supported by the ANSI terminal expansion
#
# The 256 colors are arranged in 3 groups...
#
# 16 System Colors  codes 0 to 15     (standard, then hi-intensity)
# 6x6x6 Color Cube  codes 16 to 231   (16 + r*36 + g*6 + b, for values 0-5)
# a greyscale ramp  codes 232 to 255  (24 step greysacle, exclude min/max)
#
# and are used using   "\e[38;5;${code}m"  for the foreground color
# and are used using   "\e[48;5;${code}m"  for the background color
#
# Some terminals allow you to specify the nearest color to RGB values
# (including xterm and konsole)  "\e[38;2;$R;$G;$B"
#
# XTERM color settings in the 6x6x6 cube is not particularly well defined
#
e=$'\e'            # Escape character
F=$'\e[0;38;5;%dm' # set background color and output two spaces
B=$'\e[0;48;5;%dm' # set background color and output two spaces
N=$'\e[0m'         # reset to normal

echo "For 8-bit color table Xterms..."
echo "  \$'\e[48;5;{color}m'     to set background color"
echo "  \$'\e[38;5;{color}m'     to set the foreground color"
echo "For direct 24-bit color Xterms (from 2019)..."
echo "  \$'\e[38;2;{R};{G};{B}m' to set a specific RGB color"
echo "Reset color (as always)..."
echo "  \$'\e[0m'                to return to normal"

echo ""
echo ""
echo "System Colors: (codes 0 to 15)"

for j in `seq 0 1`; do
  for i in `seq 0 7`; do
    c=$((i+j*8))
    printf "$B  " $c
  done
  printf "$N\n"
done
echo "These are also available via older ANSI color codes."
echo "And some are also duplicated in the color cube below."

echo "NOTE: the blue is not a perfect blue in xterms!"
echo ""

echo "6x6x6 RGB Color Cube:"
echo "using  \$'\e[48;5;{color}m'  color codes 16 to 231"

for k in `seq 0 5`; do
  for j in `seq 0 5`; do
    for i in `seq 0 5`; do
      c=$((16+i+k*6+j*36))
      printf "$B  " $c
    done
    printf "$N "
  done
  printf "\n"
done
printf "\n"

echo "16 shade Greyscale Ramp:"
echo "using  \$'\e[48;5;{color}m'  color codes 232 (black) to 255 (white) )"

printf "$B   " 0
for i in `seq 232 255`; do
  printf "$B   " $i
done
printf "$B   $N\n" 15
printf "\n"

echo "Rough Name Matches for colors:"
printf "$B      $F  36 Sea Green      "  36  36;
printf "$B      $F  39 Light Blue     "  39  39;
printf "$B      $F  45 Near Cyan      "  45  45;
printf "\n";
printf "$B      $F 130 Brown          " 130 130;
printf "$B      $F 202 Orange         " 202 202;
printf "$B      $F 199 Hot Pink       " 199 199;
printf "\n";
printf "$B      $F  52 Firebrick      "  52  52;
printf "$B      $F  93 Purple         "  93  93;
printf "$N\n";
printf "\n";

printf "%s\n%s\n" \
   'Example compare cyan (6), with near-cyan (45), with bright cyan (14)' \
   "echo \$'\\e[48;5;6m    \\e[48;5;45m    \\e[48;5;14m    \\e[0m'"
echo $'\e[48;5;6m    \e[48;5;45m    \e[48;5;14m    \e[0m'
echo