Add colors-256 script

home/packages/cli/scripts/default.nix

@@ -8,5 +8,6 @@ in {
     home.packages = with scriptPkgs; [
       bitcoin
       cheatsh
+      colors256
     ];
 }

home/packages/cli/scripts/packages/colors256/colors-256.sh

@@ -0,0 +1,101 @@
+#!/usr/bin/env bash
+
+# # Print out 256 colors, with each number printed in its corresponding colour
+#
+# This file is uploaded on <https://gist.githubusercontent.com/HaleTom/89ffe32783f89f403bba96bd7bcd1263/raw/>
+# It was originally intended to be used as an alias that curled this URL and piped it into bash, however
+# this is very unsafe as the owner can change the content of this gist at his convenience, meaning it was
+# a potential security vulnerability. This is a script version of this alias to avoid this issue.
+#
+# The copyright for this file belongs to the original author: Tom Hale, 2016
+# This file was released under MIT license
+
+set -eu # Fail on errors or undeclared variables
+
+printable_colours=256
+
+# Return a colour that contrasts with the given colour
+# Bash only does integer division, so keep it integral
+function contrast_colour {
+  colour="$1"
+
+  if ((colour < 16)); then # Initial 16 ANSI colours
+    ((colour == 0)) && printf "15" || printf "0"
+    return
+  fi
+
+  # Greyscale # rgb_R = rgb_G = rgb_B = (number - 232) * 10 + 8
+  if ((colour > 231)); then # Greyscale ramp
+    ((colour < 244)) && printf "15" || printf "0"
+    return
+  fi
+
+  # All other colours:
+  # 6x6x6 colour cube = 16 + 36*R + 6*G + B  # Where RGB are [0..5]
+  # See http://stackoverflow.com/a/27165165/5353461
+
+  # r=$(( (colour-16) / 36 ))
+  g=$((((colour - 16) % 36) / 6))
+  # b=$(( (colour-16) % 6 ))
+
+  # If luminance is bright, print number in black, white otherwise.
+  # Green contributes 587/1000 to human perceived luminance - ITU R-REC-BT.601
+  ((g > 2)) && printf "0" || printf "15"
+  return
+
+  # Uncomment the below for more precise luminance calculations
+
+  # # Calculate percieved brightness
+  # # See https://www.w3.org/TR/AERT#color-contrast
+  # # and http://www.itu.int/rec/R-REC-BT.601
+  # # Luminance is in range 0..5000 as each value is 0..5
+  # luminance=$(( (r * 299) + (g * 587) + (b * 114) ))
+  # (( $luminance > 2500 )) && printf "0" || printf "15"
+}
+
+# Print a coloured block with the number of that colour
+function print_colour {
+  local colour="$1" contrast
+  contrast=$(contrast_colour "$1")
+  printf "\e[48;5;%sm" "$colour"                # Start block of colour
+  printf "\e[38;5;%sm%3d" "$contrast" "$colour" # In contrast, print number
+  printf "\e[0m "                               # Reset colour
+}
+
+# Starting at $1, print a run of $2 colours
+function print_run {
+  local i
+  for ((i = "$1"; i < "$1" + "$2" && i < printable_colours; i++)); do
+    print_colour "$i"
+  done
+  printf "  "
+}
+
+# Print blocks of colours
+function print_blocks {
+  local start="$1" i
+  local end="$2" # inclusive
+  local block_cols="$3"
+  local block_rows="$4"
+  local blocks_per_line="$5"
+  local block_length=$((block_cols * block_rows))
+
+  # Print sets of blocks
+  for ((i = start; i <= end; i += (blocks_per_line - 1) * block_length)); do
+    printf "\n" # Space before each set of blocks
+    # For each block row
+    for ((row = 0; row < block_rows; row++)); do
+      # Print block columns for all blocks on the line
+      for ((block = 0; block < blocks_per_line; block++)); do
+        print_run $((i + (block * block_length))) "$block_cols"
+      done
+      ((i += block_cols)) # Prepare to print the next row
+      printf "\n"
+    done
+  done
+}
+
+print_run 0 16 # The first 16 colours are spread over the whole spectrum
+printf "\n"
+print_blocks 16 231 6 6 3   # 6x6x6 colour cube between 16 and 231 inclusive
+print_blocks 232 255 12 2 1 # Not 50, but 24 Shades of Grey

home/packages/cli/scripts/packages/colors256/default.nix

@@ -0,0 +1,9 @@
+{pkgs, ...}:
+(pkgs.writeShellApplication {
+  name = "colors-256";
+  runtimeInputs = with pkgs; [coreutils];
+  text = ''
+    ${builtins.readFile ./colors-256.sh}
+  '';
+})
+

home/packages/cli/scripts/packages/default.nix

@@ -5,6 +5,7 @@
   packages = {
     bitcoin = pkgs.callPackage ./bitcoin.nix {};
     cheatsh = pkgs.callPackage ./cheatsh {};
+    colors256 = pkgs.callPackage ./colors256 {};
   };
 in
   packages