scripts: add 24-bit color test script

24-bit-color-test.sh

@@ -0,0 +1,92 @@
+#!/usr/bin/env bash
+#
+#   This file echoes a bunch of 24-bit color codes
+#   to the terminal to demonstrate its functionality.
+#   The foreground escape sequence is ^[38;2;<r>;<g>;<b>m
+#   The background escape sequence is ^[48;2;<r>;<g>;<b>m
+#   <r> <g> <b> range from 0 to 255 inclusive.
+#   The escape sequence ^[0m returns output to default
+
+setBackgroundColor() {
+    echo -en "\x1b[48;2;$1;$2;$3""m"
+}
+
+resetOutput() {
+    echo -en "\x1b[0m\n"
+}
+
+# Gives a color $1/255 % along HSV
+# Who knows what happens when $1 is outside 0-255
+# Echoes "$red $green $blue" where
+# $red $green and $blue are integers
+# ranging between 0 and 255 inclusive
+rainbowColor()
+{
+    h=$(($1 / 43))
+    f=$(($1 - 43 * h))
+    t=$((f * 255 / 43))
+    q=$((255 - t))
+
+    if [ "$h" -eq 0 ]; then
+        echo "255 $t 0"
+    elif [ "$h" -eq 1 ]; then
+        echo "$q 255 0"
+    elif [ "$h" -eq 2 ]; then
+        echo "0 255 $t"
+    elif [ "$h" -eq 3 ]; then
+        echo "0 $q 255"
+    elif [ "$h" -eq 4 ]; then
+        echo "$t 0 255"
+    elif [ "$h" -eq 5 ]; then
+        echo "255 0 $q"
+    else
+        # execution should never reach here
+        echo "0 0 0"
+    fi
+}
+
+for i in $(seq 0 127); do
+    setBackgroundColor "$i" 0 0
+    echo -en " "
+done
+resetOutput
+for i in $(seq 255 -1 128); do
+    setBackgroundColor "$i" 0 0
+    echo -en " "
+done
+resetOutput
+
+for i in $(seq 0 127); do
+    setBackgroundColor 0 "$i" 0
+    echo -n " "
+done
+resetOutput
+for i in $(seq 255 -1 128); do
+    setBackgroundColor 0 "$i" 0
+    echo -n " "
+done
+resetOutput
+
+for i in $(seq 0 127); do
+    setBackgroundColor 0 0 "$i"
+    echo -n " "
+done
+resetOutput
+for i in $(seq 255 -1 128); do
+    setBackgroundColor 0 0 "$i"
+    echo -n " "
+done
+resetOutput
+
+for i in $(seq 0 127); do
+    # shellcheck disable=SC2046
+    setBackgroundColor $(rainbowColor "$i")
+    echo -n " "
+done
+resetOutput
+for i in $(seq 255 -1 128); do
+    # shellcheck disable=SC2046
+    setBackgroundColor $(rainbowColor "$i")
+    echo -n " "
+done
+resetOutput